# Estimating extra reach (resolving power) of crop vs FF



## AlanF (Aug 27, 2014)

Here is a way of calculating the effective extra reach or resolving power of a crop body versus FF, which will amuse the geeks among us.

Measure the MTF of a lens on the crop (= MTFcrop) and the same lens on the FF (= MTFff). The ratio of the MTFs, MTFcrop/MTFff, gives the relative resolving power of the bodies with that lens. However, the crop body can be placed 1.6x further away to give the same field of view. Therefore, the true effective relative resolving power, R, is given by:

R = 1.6x MTFcrop/MTFff.

Photozone lists measured MTFs for a set of lenses on the 5DII and 50D. I calculated their ratios for the Canon 200mm f/2.8 II, 85mm f/1.2 II and 35mm f/2 at wide apertures below the DLA. MTFcrop/MTFff is very close to 0.726 in all cases.

This gives R for 50D/5DII = 1.16.

So the effective extra reach is 16%. (Based on the ratio of their pixel sizes, a value of 36% is expected.

The dpreview widget gives values for the 5DIII and 7D only for a few lenses. I did the same calculations with the Tamron 150-600mm (between 150-400mm), the Canon 200-400mm and the Sigma 50mm f/1.4 A at wider apertures below the DLA. In all cases, MTFcrop/MTFff is close to 0.742.

This gives R for 7D/5DIII = 1.19.

So, the effective extra reach is 19%. (Based on the ratio of their pixel sizes, a value of 45% is expected).

There are always arguments about using MTFs quantitatively, but I think in this particular calculation it is reasonably valid to use them. It fits in reasonably well with experience - Jon has shown there is better resolving power in photos of the moon with the 7D, but it doesn't look 45% better. And my own experience is that the 7D and 70D aren't much better than the 5DIII, certainly not 1.6x.


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## privatebydesign (Aug 27, 2014)

That might be true in a testing scenario, but few of us shoot in those. Factor in AF, handholding, higher than base iso, less than ideal aperture or shutter speed etc etc etc and the differences become minimal, as so many people who have owned both have attested to.

That doesn't mean there is no point to a 7D, 70D 7D MkII, as a compliment to a 6D etc one might work very well, but the resolution thing really is a red herring unless you are using a heavy tripod, 10X live view manual focus blah blah.........


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## Deleted member 91053 (Aug 27, 2014)

I have found little difference in reach when changing sensor size, though I have noticed improved IQ.
I don't carry out scientific comparisons I just go out and see which performs better.
I do most of my photography with the Canon 800mm so if there were much of a difference this is the lens to show it up!
Now if Canon/Nikon made a low MP APSC camera to the same standard as the 1DX/D4 then the situation may be different!


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## AlanF (Aug 27, 2014)

privatebydesign said:


> That might be true in a testing scenario, but few of us shoot in those. Factor in AF, handholding, higher than base iso, less than ideal aperture or shutter speed etc etc etc and the differences become minimal, as so many people who have owned both have attested to.
> 
> That doesn't mean there is no point to a 7D, 70D 7D MkII, as a compliment to a 6D etc one might work very well, but the resolution thing really is a red herring unless you are using a heavy tripod, 10X live view manual focus blah blah.........



What the estimates tell you is that even if you have a heavy tripod, base iso etc you will gain only a small increase in reach, and not 60%.


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## neuroanatomist (Aug 28, 2014)

AlanF said:


> This gives R for 7D/5DIII = 1.19.
> 
> So, the effective extra reach is 19%. (Based on the ratio of their pixel sizes, a value of 45% is expected).





privatebydesign said:


> That might be true in a testing scenario, but few of us shoot in those. Factor in AF, handholding, higher than base iso, less than ideal aperture or shutter speed etc etc etc and the differences become minimal, as so many people who have owned both have attested to.



As I've stated, the most significant advantage to APS-C is *lower cost*.


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## privatebydesign (Aug 28, 2014)

AlanF said:


> privatebydesign said:
> 
> 
> > That might be true in a testing scenario, but few of us shoot in those. Factor in AF, handholding, higher than base iso, less than ideal aperture or shutter speed etc etc etc and the differences become minimal, as so many people who have owned both have attested to.
> ...



I've been saying that for years and practically nobody agreed with me, it is great to see the winds of change, finally. 

I deliberately stayed out of the last 5D MkIII and 7D reach comparison thread, it was interesting that after ironing out some flawed methodology the same conclusions were drawn that I did a long time ago, albeit to the utter disdain and disbelief of the then only 7D owning OP.

I wonder if people will believe me on some of the other contentious stuff I say now too? I doubt it..........


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## AlanF (Aug 28, 2014)

I did the same calculations for the Nikon D800 and D7000. You would expect them to have virtually identical resolving powers since their pixel sizes are 4.88 and 4.78 µM, respectively. And that is what I calculated, giving some credence to the calculations I did for the Canons.

MTFcrop/MTFff with identical lenses is close to 0.63 for all lenses (on the dpr widget), compared with 0.66 expected from the relative pixel heights of both sensors. The relative resolving power of the crop, given the 1.5x less field of view is:

R = 0.945 (compared with R= 1.02, calculated from the ratio of pixel sizes).

The 36.6 mpx ff beats out the 16 mp crop since, when cropped it is at least as good as the crop sensor and has all the advantages of FF when not cropped.


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## AcutancePhotography (Aug 28, 2014)

privatebydesign said:


> I wonder if people will believe me on some of the other contentious stuff I say now too? I doubt it..........



If you support your opinions with evidence that can be independently evaluated... yes
If you just state your opinion... no


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## FEBS (Aug 28, 2014)

AlanF said:


> The dpreview widget gives values for the 5DIII and 7D only for a few lenses. I did the same calculations with the Tamron 150-600mm (between 150-400mm), the Canon 200-400mm and the Sigma 50mm f/1.4 A at wider apertures below the DLA. In all cases, MTFcrop/MTFff is close to 0.742.
> 
> This gives R for 7D/5DIII = 1.19.
> 
> ...



So if the new 7D2 might have a 20.2mp in stead of 18mp of 7D then the effective extra reach would be about 25% roughly?

That makes me think about my idea of buying the 7D2. My extra reach will not be that high as expected. Truly, that was something I did find remarkable after I bought a 5D3, that I could crop much more compared to the 7D. This should be the scientific prove for that. If It was really a 1.6 factor, then the details should also stay more present in the photo, and that's not the same if you compare in Lightroom for both cameras. The 5D3 gives more possibility to crop, so that in practice the 60% is only 19% in advance for the 7D.

For sure something to keep in mind.

Thanks for this explanation Alan.


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## Mt Spokane Photography (Aug 28, 2014)

AlanF said:


> I did the same calculations for the Nikon D800 and D7000. You would expect them to have virtually identical resolving powers since their pixel sizes are 4.88 and 4.78 µM, respectively. And that is what I calculated, giving some credence to the calculations I did for the Canons.
> 
> MTFcrop/MTFff with identical lenses is close to 0.63 for all lenses (on the dpr widget), compared with 0.66 expected from the relative pixel heights of both sensors. The relative resolving power of the crop, given the 1.5x less field of view is:
> 
> ...



The issue with the D800 was that even carefully done tests by experienced testers, DPR, for example, had to use extreme measures to get the resolution the sensor is capable of. Ordinary users do not stand a chance, since even the tiniest vibration blurs some of the pixels. You must use high shutter speeds, and for telephoto shots, where you want more reach, its even more difficult. Turn up the ISO so you can use a faster shutter speed, stop down to increase lens resolution, and you loose resolution due to noise.

The gain is real, but almost unattainable, even by experts.


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## NancyP (Aug 28, 2014)

Don't knock "lower cost", not to mention lower weight. Not everyone is going to be forking over $6,600.00 for an action camera. A reasonably priced "mini-1DX"-spec'ced (wrt fps and buffer) 7D2 is a very attractive compromise for those who ALSO don't have a Big White yet.


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## privatebydesign (Aug 28, 2014)

Nancy, nobody does.

And focal length limited doesn't mean there isn't a lens available, it just means you don't have it to use, it doesn't matter if you don't own it or you don't have it with you. 

I rarely take longer than a 70-200 with me unless I know I will need it, but that 200 is my limit whether I have a 7D or a 5D MkIII. AlanF has given us a sound mathematical explanation as to why the pixel numbers don't add up to the resolution differences we see.

My take was back in the 7D and 5D MkII days when people owned both because they thought the 7D gave them a lot more resolution over a cropped 5D MkII, but it doesn't, it does give them better AF and frame rate, but not a noticeable increase in resolution from real world shooting. My suggestion at that time to people wanting a 5D MkII and a 7D was to not get either but get a 1Ds MkIII instead, it covered both cameras stills capabilities for around the same money. AlanF has just presented us with a real equation as to why the "pixels on duck" meme was a complete fallacy.


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## RustyTheGeek (Aug 28, 2014)

NancyP said:


> Don't knock "lower cost", not to mention lower weight. Not everyone is going to be forking over $6,600.00 for an action camera. A reasonably priced "mini-1DX"-spec'ced (wrt fps and buffer) 7D2 is a very attractive compromise for those who ALSO don't have a Big White yet.



LOL *Nancy*! ;D Funny, I was thinking the same thing! I really like *nuero* but it's easy to make his statement when one owns the gear he does. (And over the years I've spent more than I care to admit as well.)

Note: I just purchased a Canon Refurb 70D 18-55 Kit for $836 from Canon because I don't want to spend the huge $$ on the likely over $2K 7D2. (And I think it will likely follow the same path as the previous 7D/60D releases and have a similar if not the same sensor anyway.) My reason? More reach with better crop sensor and higher fps (than the 60D). That's about it.


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## wsmith96 (Aug 28, 2014)

AlanF said:


> privatebydesign said:
> 
> 
> > That might be true in a testing scenario, but few of us shoot in those. Factor in AF, handholding, higher than base iso, less than ideal aperture or shutter speed etc etc etc and the differences become minimal, as so many people who have owned both have attested to.
> ...



edited for asking my question within the quote - sorry

Reach or resolution?


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## AlanF (Aug 28, 2014)

wsmith96 said:


> AlanF said:
> 
> 
> > privatebydesign said:
> ...



In the following context they are the same: if you can achieve 1.6x greater resolution with the crop, a subject 1.6x further away will have the same apparent resolution as for the FF and so you have 1.6x the reach.


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## privatebydesign (Aug 28, 2014)

It is a great shame you chose 1.6 as your example number there Alan, it will confuse people all the more as it is the "crop factor". 

You point out that the difference in resolution is between 1.19 and 1, depending on the sensors being compared, that is the point, the best you can hope for with a crop camera is between nothing and 19% more "reach", not the 60% that last comment implies.


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## Andyx01 (Aug 28, 2014)

I'm sure this thread is full of bad information all around, and I'm not even going to read the previous posts.
If you want to know how to convert back and forth here are the facts.

FF is 2.56X larger than APSC (1.6X crop factor - 1.6 * 1.6 = 2.56)
If you have an APSC Body with a given lens, and want to obtain the same framing, depth of field, and ISO noise on a FF use the following math:
Crop to Full Frame:
Length * 1.6
Aperature * 1.6
ISO * 2.56

i.e. a
100mm f/2.8 lens @ ISO 400 on a Crop body camera will take the same picture as
160mm f/4.48 lens @ ISO 1024 on a Full Frame body.

To convert the other way, the math is:
Length / 1.6
Aperature / 1.6
ISO / 2.56

i.e. a Full Frame with an 85mm f/1.8 lens shooting at ISO 320 =
a Crop body 53mm f/1.1 lens shooting at ISO 125

As far as cropping a Full frame image down to an APSC size, the pixels on target are FF MP divided by 2.56
i.e. 22MP / 2.56 = roughly 8.6MP on target.

If your lens has the resolving power to see the added resolution, then there ya go, use a crop body for extra reach.


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## privatebydesign (Aug 28, 2014)

Andyx01 said:


> I'm sure this thread is full of bad information all around, and I'm not even going to read the previous posts.
> If you want to know how to convert back and forth here are the facts.
> 
> FF is 2.56X larger than APSC (1.6X crop factor - 1.6 * 1.6 = 2.56)
> ...



Well maybe you should have read some of it Andy, if you had you would have realised we are not talking about equivalence, which you have outlined reasonable well. We are talking about comparable resolution capabilities, the bit you sum up as _"If your lens has the resolving power to see the added resolution"_, that is the bit we are talking about.


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## AlanF (Aug 28, 2014)

Andyx01 said:


> I'm sure this thread is full of bad information all around, and I'm not even going to read the previous posts.



What can one say to that?


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## Don Haines (Aug 28, 2014)

AlanF said:


> Andyx01 said:
> 
> 
> > I'm sure this thread is full of bad information all around, and I'm not even going to read the previous posts.
> ...


I can say "go get an SX-50"


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## Deleted member 91053 (Aug 29, 2014)

Come on folks!
Quoting all the whizz bang factors and theoretical pro's and cons means precisely nothing!
Get out and shoot some shots with the various sensor sizes and see which works for you. 
The last comparative trial I did was to try a friends 7D on my Canon 800 F5.6 L IS, at the time had just bought a 1DX and still had my 1D4. All cameras were set the same for metering. shutter speed, aperture etc. As expected the 7D and 1D4 made the subject (a co-operative Moorhen) larger in the frame but the 1DX gave significantly more pleasing images. Note the bird was stationery so not an AF test.
True this was far from a scientific experiment but who cares - I certainly don't! Since moving to exclusively full frame I am getting more keepers and better ones at that, yes I do have to crop a little more with my 1DX but the files hold up much better than the other 2 cameras.
Try them out for yourself and see and if you prefer camera X then go for it. For me, being focal length challenged, I prefer the results that I am getting with my full frame camera, after all it is only 90% reach - that other 10% makes all the difference!


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## jrista (Aug 29, 2014)

AlanF said:


> Here is a way of calculating the effective extra reach or resolving power of a crop body versus FF, which will amuse the geeks among us.
> 
> Measure the MTF of a lens on the crop (= MTFcrop) and the same lens on the FF (= MTFff). The ratio of the MTFs, MTFcrop/MTFff, gives the relative resolving power of the bodies with that lens. However, the crop body can be placed 1.6x further away to give the same field of view. Therefore, the true effective relative resolving power, R, is given by:
> 
> ...




Interesting stuff! I think it's a useful formula...and I think it gives realistic results that mirror my experiences.



AlanF said:


> There are always arguments about using MTFs quantitatively, but I think in this particular calculation it is reasonably valid to use them. It fits in reasonably well with experience - Jon has shown there is better resolving power in photos of the moon with the 7D, but it doesn't look 45% better. And my own experience is that the 7D and 70D aren't much better than the 5DIII, certainly not 1.6x.



I think your numbers jive with my experiences, and perceptually the difference between the moon photos I shared on my thread about reach limited resolving power seems to be about 20%.

I think we need to be honest about what that means, though. If we were talking about 3-5%, which is often the margin of error of these kinds of calculations (since they are based of of empirical data), then I would agree...the difference would effectively be "meaningless" or "irrelevant".

However...between the 7D and 5D III, or the 70D and 5D III for that matter (and possibly the 7D II and 5D III even), were talking about a TWENTY PERCENT DIFFERENCE. Twenty percent! That's a pretty big difference. It's well beyond the margin of error. I usually use the term "meaningful difference" myself...and I would call a 20% difference meaningful. 

I spent many years of my younger days overclocking CPUs. I spent huge sums of money buying the latest and greatest, top of the line CPUs, I water cooled (still do, actually), I overclocked. All for a few percent gain in performance, all to top the 3DMark charts or CPU benchmark. The reduction in times between executing certain tasks, such as ripping music or encoding video or playing games was often meaningful as well. Before a new CPU or an overclock, it might have frequently been the case that playing Game XYZ would drop below the 30fps limit, where frame stutter would start showing up...and that extra 5-8% worth of processing power from the new CPU or overclock would tip the scales and keep the games frame rate over 30fps. When a new CPU came out that had a 10% improvement in performance over the prior "top of the line" competitor, it was really huge news! That meant just buying the new CPU meant your Game XYZ performance would top 30fps, and you could then overclock, and get that minimum frame rate even higher! (Ah, the good ol' days of early 3D PC gaming... *memories* )

Were talking about precision devices here. The differences are never going to be massive. A 50% difference between two sensors would be truly massive, and more than just a "meaningful difference"...it would be a very obvious, very significant difference. It would be truly game-changing. Two additional stops of DR on the D800 was game changing (as much as people here don't like to admit it...it really was). Were not talking about that kind of difference in resolution between APS-C and FF most of the time...but, neither are we talking about a _meaningless _difference. 

*It's twenty percent.* _That's meaningful._ _It's visible._ Assuming that you hand-hold a 5D III the same way you hand-hold a 7D, all else being equal (i.e. assuming you lock on AF and are successfully tracking your subject)...any issues introduced by hand-holding the cameras don't actually have anything to do with the cameras. A small amount of camera shake is going to affect the images of both...especially if your already resolution-limited on the sensor with bigger pixels (it's the same angular movement regardless, and since your reach limited...I don't see why it would affect one less than the other unless the movement was VERY small...say 1/3rd the size of a pixel or less, however then, the impact to IQ is going to be minuscule anyway.)


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## Jack Douglas (Aug 29, 2014)

I'm with Jon on the comments of 20% being meaningful. When I spent $7k on the 300 2.8 II I immediately compared it to my 70-300 Nikon zoom on the D5100 and was quite disappointed to see the 300 really didn't outperfom it by much mounted on my 6D - that is relative to resolution of detail. However, it has proved to be an awful lot better in other respects and I'm happy with it.

My friend was waiting to purchase and we beat all this to death. My comment to him was that all those thousands of $$ were going into making a lens that was "maybe 20% better". I value that "maybe 20% better".

Jack


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## AlanF (Aug 29, 2014)

Thanks Jon. What I tried to do was put some numbers behind the long running debate and help me in my choice of gear. 20% is the difference between a 600mm and a 500mm lens, which is useful, but a 500 on a crop is not equivalent to an 800 on FF in terms of resolution.

I am very happy with both my 5DIII and 70D. For much of my time, I take bird photos where the little charmers occupy far less than the crop sensor area and so the 70D represents phenomenal value. For birds in flight, the 1.6x wider field of view for the same lens makes it easier with the FF. And, as others point out, FF is less demanding for hand-held work. The factor of 1.6 in field of view increases the effects of camera shake by approximately 60% for crop for a gain of 20% gain in resolution.


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## LetTheRightLensIn (Aug 29, 2014)

privatebydesign said:


> That might be true in a testing scenario, but few of us shoot in those. Factor in AF, handholding, higher than base iso, less than ideal aperture or shutter speed etc etc etc and the differences become minimal, as so many people who have owned both have attested to.



If by so many people you mean yourself and two people on FM. So three people.


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## LetTheRightLensIn (Aug 29, 2014)

privatebydesign said:


> AlanF said:
> 
> 
> > privatebydesign said:
> ...



Less so, since my 'lab' test and field experience with 7D (before I sold it off) and 5D2/5D3 very much told me otherwise. And same goes for the accomplished bird photography Romy who posts here from time to time.


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## LetTheRightLensIn (Aug 29, 2014)

Andyx01 said:


> I'm sure this thread is full of bad information all around, and I'm not even going to read the previous posts.
> If you want to know how to convert back and forth here are the facts.
> 
> FF is 2.56X larger than APSC (1.6X crop factor - 1.6 * 1.6 = 2.56)
> ...



not if you are reached limited, for FOV yeah it's just 1.6xs factor, but that is meaningless when the goal is to get pixels on something far away, FOV doesn't matter at all


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## Andyx01 (Aug 29, 2014)

We are talking about comparable resolution capabilities, the bit you sum up as _"If your lens has the resolving power to see the added resolution"_, that is the bit we are talking about.
[/quote]

I fail to see why crop v.s. FF is part of this topic when you clearly and accurately suggested it is about sensor density v.s. lens resolving power. The original author might as well have posted "Estimating extra reach (resolving power) of Canon v.s. Sony. - Makes as much sense.

Which brings us full circle - There is no extra 'reach' on Crop v.s. Full Frame, the diffraction limits are the same either way.

The Subject should read:"Estimating extra reach (resolving power) increased sensor densities provide for a given lens.


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## jrista (Aug 29, 2014)

Andyx01 said:


> > We are talking about comparable resolution capabilities, the bit you sum up as _"If your lens has the resolving power to see the added resolution"_, that is the bit we are talking about.
> 
> 
> 
> ...



It doesn't really matter what the title of the thread is. The simple FACT of the matter is that smaller sensors nearly universally have smaller pixels than larger sensors. ONE large sensor has a lot of pixels, the 36.3mp Exmor, however even it's pixels are still larger than the pixels on the vast majority of modern day crop cameras. It doesn't matter if we call it "Estimating the extra reach of crop vs FF" or "Estimating the extra reach of small vs. large pixels". That's quibbling over semantics. Since smaller sensors are nearly guaranteed to have smaller pixels, the current title works fine.

Next, however, the whole notion that either a lens or sensor "sees" the resolving power of the other is a fallacy. I've explained this countless times on these forums, but here it goes again.

OUTPUT RESOLUTION (the measurable resolution of the image produced by a CAMERA, for the purposes of this post, defined as Lens+Sensor), is the CONVOLUTION of the resolution of the real scene as it's light passes through the lens and is recorded by the sensor. That's the key word here, convolution. Cameras convolve information. While it is possible for a lens to resolve 86lp/mm at f/8, and a sensor to have the ability to separate 116lp/mm, the notion that the sensor "outresolves" the lens at f/8 is a misnomer. What is really happening is the lens and sensor are working together to produce a BLUR SPOT. The size of that blur spot is what determines the resolution of the OUTPUT IMAGE.

We can very closely approximate the resolution of lenses and sensors by using the following formula:


```
blurSpot = SQRT(lensSpot^2 + sensorSpot^2)
```

The spot size of a lens can be computed by multiplying the resolving power in line pairs per millimeter, multiplying by two, and taking the reciprocal:


```
lensSpot = 1/(lensRes*2)
```

We can further convert the blur spot into spatial resolution by using the following formula:


```
spatRes = (1/blurSpot) / 2
```

We can combine these formulas into one single formula to take :


```
spatRes = (1/SQRT(lensSpot^2 + sensorSpot^2)) / 2
```

If we have a 1D X, 5D III, D800, 70D, and D5300 then (let's just assume they are monochrome sensors, for the sake of simplicity) each of those has a sensor spot of:


```
1DX: 6.92µm
5DIII: 6.25µm
D800: 4.9µm
70D: 4.16µm
D5300: 3.9µm
```

If we use the same theoretical lens, one which performs ideally at all apertures, on all five of these cameras, at apertures of f/2, f/4, and f/8, then the lenses DIFFRACTION LIMITED resolving powers are:


```
f/2: 346lp/mm
f/4: 173lp/mm
f/8: 86lp/mm
```

Converting these to spot sizes:


```
f/2: 1/(346*2) = 0.0014mm (1.4µm)
f/4: 1/(173*2) = 0.0029mm (2.9µm)
f/8: 1/(86*2) = 0.0058mm (5.8µm)
```

Running the numbers, we get the following:


```
1DX f/2: (1/SQRT(0.0014^2 + 0.00692^2)) / 2 = 71lp/mm
1DX f/4: (1/SQRT(0.0029^2 + 0.00692^2)) / 2 = 66.8lp/mm
1DX f/8: (1/SQRT(0.0058^2 + 0.00692^2)) / 2 = 55.5lp/mm

5DIII f/2: (1/SQRT(0.0014^2 + 0.00625^2)) / 2 = 107lp/mm
5DIII f/4: (1/SQRT(0.0029^2 + 0.00625^2)) / 2 = 94.6lp/mm
5DIII f/8: (1/SQRT(0.0058^2 + 0.00625^2)) / 2 = 68.6lp/mm

D800 f/2: (1/SQRT(0.0014^2 + 0.0049^2)) / 2 = 134lp/mm
D800 f/4: (1/SQRT(0.0029^2 + 0.0049^2)) / 2 = 111lp/mm
D800 f/8: (1/SQRT(0.0058^2 + 0.0049^2)) / 2 = 74lp/mm

70D f/2: (1/SQRT(0.0014^2 + 0.00416^2)) / 2 = 153.5lp/mm
70D f/4: (1/SQRT(0.0029^2 + 0.00416^2)) / 2 = 121lp/mm
70D f/8: (1/SQRT(0.0058^2 + 0.00416^2)) / 2 = 76lp/mm

D5300 f/2: (1/SQRT(0.0014^2 + 0.0039^2)) / 2 = 161.6lp/mm
D5300 f/4: (1/SQRT(0.0029^2 + 0.0039^2)) / 2 = 125lp/mm
D5300 f/8: (1/SQRT(0.0058^2 + 0.0039^2)) / 2 = 77lp/mm
```

Again, these are all theoretically diffraction limited apertures. Assuming such a case, small pixels, even the very small pixels of the D5300 are STILL resolving more detail at a diffraction limited f/8, which has a maximum theoretical resolution of 86lp/mm, than any of the full frame cameras with bigger pixels. There are diminishing returns, however the D5300 still enjoys over a 4% OUTPUT IMAGE resolution lead over the D800, and it enjoys a very large lead of 12.3% over the 5D III and a whopping 38.7% lead over the 1D X. 

This is a DIFFRACTION LIMITED sensor. The notion that a higher resolution sensor cannot benefit at fully diffraction limited, narrow apertures like f/8, is patently false. The notion that a lens that is not resolving more than the sensor "cannot see" the resolution of the sensor is patently false. The two, lens and sensor, WORK TOGETHER to produce the final output resolution. In actuality, the specifics are certainly more complicated. Lenses tend NOT to be diffraction limited at wider apertures, and optical aberrations, of which there are many that affect the convolution of the incoming wavefront in different ways, will limit resolution at wide apertures on many lenses. However the same rules apply...for any given lens spot, regardless of whether it is limited by diffraction or aberrations, is going to CONVOLVE with the sensor. Higher resolution sensors, while they will eventually reach a point of diminishing returns, are STILL going to resolve more detail than lower resolution sensors.


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## AlanF (Aug 30, 2014)

Thanks Jon for sharing your calculations. To support experimentally what you are saying about diffraction limited aperture, the Canon SX50 has 1.54 µM pixels, giving a DLA of f/2.5. Its widest aperture at f = 1200mm effective is f/6.5, 2.6 x the dla, yet it really does still out resolve most cameras with larger pixels, as Don Haines will confirm.


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## Northstar (Aug 30, 2014)

This stuff just gets too technical for me, so let me ask a question.

I'm standing on the side of the road on a sunny day and I'm looking at a bald eagle that is 75 meters away sitting at the top of a tree. In my camera bag is my 300mm 2.8 lens, a 7D and 5D3. 

I'm shooting handheld. I don't dare move closer for fear that I scare him off.

If I'm trying to produce a final/edited image that "fills the frame" with as much detail, sharpness, and overall IQ as possible, which body do I attach to the 300mm?


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## privatebydesign (Aug 30, 2014)

The 7D.


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## AlanF (Aug 30, 2014)

Northstar said:


> This stuff just gets too technical for me, so let me ask a question.
> 
> I'm standing on the side of the road on a sunny day and I'm looking at a bald eagle that is 75 meters away sitting at the top of a tree. In my camera bag is my 300mm 2.8 lens, a 7D and 5D3.
> 
> ...



A fully grown bald eagle is 1 m long. The size of the image on the sensor for a 300mm lens 75 m away is 4 mm. corresponding to 930 pixels on the 7D or 640 on the 5DIII. 300mm is too short for a decent image. I would use the 300 mm + 2xTC on either camera as 1860 px on the 7D or 1280 on the 5DIII would give an excellent image. You didn't have the 2xTC in your bag, I know but that is bad planning.


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## Northstar (Aug 30, 2014)

AlanF said:


> Northstar said:
> 
> 
> > This stuff just gets too technical for me, so let me ask a question.
> ...



Alan, my friend...I'm laughing now, didn't you see the part where I said "too technical for me".  ;D

It's a hypothetical situation. Which body should I grab?


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## Northstar (Aug 30, 2014)

privatebydesign said:


> The 7D.



Thanks PBD


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## weixing (Aug 30, 2014)

Hi,
IMHO, in the real world, it's hard to actually see the advantage of the extra resolution of the APS-C over the FF as a lot of environmental condition will limit the maximum resolution you can get... the lighting condition, air turbulence and etc. I think you can only see the advantage of the extra resolution of the APS-C over the FF is when the subject is very, very close... when all the environmental resolution "limiter" is minimize.

I had both the 60D and 6D and shoot them both together a few times and todate, I still haven't see one image from the 60D that show the advantage of the extra resolution even when pixel peeping... the subject in the 60D image is larger, but any details I can see in the 60D, I can see it in the 6D although it's smaller. 

Anyway, the only advantage I find the 60D had over the 6D is that AF is more accurate when your subject is very small... I think that may be because from the AF system point of view, the subject is bigger in the 60D, so the AF is more accurate... I also see the same result in live view AF... that's why I'm consider to change my 6D to a 7D2 when it become available... I don't print my photo, so I think I can live with the inferior high ISO performance of APS-C sensor.

Have a nice day.


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## sanj (Aug 30, 2014)

Sunny day is the key point. 7D.


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## Sporgon (Aug 30, 2014)

This really has me baffled.
85mm f1.8 @ f4, 1/1250. ISO 100
Shot on 5DII and 1100D. The crop camera down sampled to match 5D as that camera works out at about 8.5 mp when cropped and the 1100D is a 12 mp aps camera. Hand held, but had to resort to live view focusing as I couldn't believe the results.

100% crops from each camera.


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## dak723 (Aug 30, 2014)

Real world experience when I went full frame resulted in the following conclusions: The extra reach of my old crop camera produced better pictures because I could 1) see the subject larger in the viewfinder thus knowing when best to snap the pictures and 2) framed the subject larger giving me the exact (or closer to the end result) composition in the viewfinder. While cropping usually results in the same or similar composition, it doesn't always since some element that may look fine when I see it safely within the frame is now poorly placed compositionally when cropped - perhaps too near the edge of the cropped final image. 

Both of those factors are more important to me in the final analysis. Making sure I can more accurately see the subject (in terms of facial expressions. head angle, etc., and compositional accuracy. If the sharpness or resolving power is reasonably close between cameras (even if the FF is slightly better), then I will still choose the crop camera for the above reasons.


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## AlanF (Aug 30, 2014)

Northstar said:


> AlanF said:
> 
> 
> > Northstar said:
> ...



OK I'll leave out the technical stuff for you: 75 m is too far away for a 300mm for good photos of anything smaller than an ostrich so my answer is grab neither and just enjoy looking at the eagle. But, if all you want is to publish a thumbnail on the web, it won't make much difference whatever you choose.


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## Sporgon (Aug 30, 2014)

I tried up sampling the smaller file, which I don't think is really appropriate unless you're going to be enlarging beyond 100%. Even so I would still conclude that the 12 mp crop offers nothing over the 21.7 cropped to APS-c ( 8.5 mp). Perhaps this fits in with AlanF's formula.


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## Northstar (Aug 30, 2014)

AlanF said:


> Northstar said:
> 
> 
> > AlanF said:
> ...



same situation...except I'm looking at an Ostrich. Which camera do I grab.


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## neuroanatomist (Aug 30, 2014)

Northstar said:


> Northstar said:
> 
> 
> > I'm standing on the side of the road on a sunny day and I'm looking at a bald eagle that is 75 meters away *sitting at the top of a tree.*
> ...



Doesn't matter, but you'd better be on the phone to the Guinness Book of World Records, the local news media, and the tabloids to report your flying ostrich!!!


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## Northstar (Aug 30, 2014)

neuroanatomist said:


> Northstar said:
> 
> 
> > Northstar said:
> ...



lol...good one Neuro! ;D


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## Valvebounce (Aug 31, 2014)

Hi Neuro, Northstar. 
The ostrich never flew, it just walked up the tree when when it was frightened by the bald eagle! 

Cheers, Graham. 



neuroanatomist said:


> Northstar said:
> 
> 
> > Northstar said:
> ...


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## Andyx01 (Sep 2, 2014)

privatebydesign said:


> The 7D.



Are we assuming the 'scene' is un-important and the "final image that fills the frame" is to consist of just the bird itself?

The 7D will have more pixels on target, but on a cropped field.

If your cropping the image down, the 7D will have more 'resolution' - but it might not be useful resolution depending on dozens of factors.

I had a 7D, and have a 5D III. I did some tests where I cropped the 5D III to APSC frame-size and although lower in resolution, I saw no decernible differences with my sharpest lens.


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## Andyx01 (Sep 2, 2014)

Sporgon said:


> This really has me baffled.
> 85mm f1.8 @ f4, 1/1250. ISO 100
> Shot on 5DII and 1100D. The crop camera down sampled to match 5D as that camera works out at about 8.5 mp when cropped and the 1100D is a 12 mp aps camera. Hand held, but had to resort to live view focusing as I couldn't believe the results.
> 
> 100% crops from each camera.



Crop-A appears to have less dynamic range / poor shadow detail.

What can't you beleive about the results?


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## Skulker (Sep 2, 2014)

Andyx01 said:


> The 7D will have more pixels on target, but on a cropped field.
> 
> If your cropping the image down, the 7D will have more 'resolution' - but it might not be useful resolution depending on dozens of factors.
> 
> I had a 7D, and have a 5D III. I did some tests where I cropped the 5D III to APSC frame-size and although lower in resolution, I saw no decernible differences with my sharpest lens.




That's what I find. I don't see the "extra reach of crop vs FF" in the real world. I see lots of people who are convinced and try to prove it. But I have no regrets about having sold my 7D. 


The 7D was and is a great camera but I get better results from the 5D3 and the 1Dx.


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## Sporgon (Sep 2, 2014)

Andyx01 said:


> Sporgon said:
> 
> 
> > This really has me baffled.
> ...



I remember being able to see the difference in resolution between an eight mp APS camera and a twelve mp, but in this instance when comparing 8.5 of the 5DII against the 12 of APS there is no appreciable difference. 

Don't read too much into shadow detail etc, the cameras were not identically matched.


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## jrista (Sep 2, 2014)

Skulker said:


> Andyx01 said:
> 
> 
> > The 7D will have more pixels on target, but on a cropped field.
> ...



Are you sure you aren't compensating for the reach difference? Most of the claims about full frame being better are just personal feeling about how their photos actually turn out. I suspect most of the time, framing, and therefor pixels on target, is a bit better with full frame than with APS-C, thus negating the issue. I know that with my 5D III, I'm now using 1200mm f/8 more often, which completely negates any reach advantage the 7D had. Total amount of light falling on the sensor is just a little more than the 7D, so overall noise is similar...but the greater pixel count ultimately results in sharper, crisper detail in the end. (The greater pixel count also means NR is more effective, as it can be utilized more appropriately.)

Now, when it comes to shooting at 600mm f/4 on either camera, my 7D definitely resolves more detail, no question. However, I'm also definitely reach limited at that point unless I risk scaring off my subjects to get closer.


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## Skulker (Sep 2, 2014)

jrista said:


> Skulker said:
> 
> 
> > Andyx01 said:
> ...




Yes I am sure. That's why I said it and yes I am sure I am not mis compensating for reach difference. You do make some rude comments and that was one of them. You are very arrogant to imply I am incapable of making a valid comparison.


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## Stu_bert (Sep 2, 2014)

AlanF said:


> Northstar said:
> 
> 
> > This stuff just gets too technical for me, so let me ask a question.
> ...



Alan - out of curiosity, what's the maths behind subject size, lens, distance, size on sensor please? I've always wanted to be able to calculate this.

Is it focal length/(distance/subject size) = size on sensor? 

Thanks in advance.


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## jrista (Sep 2, 2014)

Skulker said:


> jrista said:
> 
> 
> > Skulker said:
> ...



It was a general statement, not about you personally, but people in general who make general claims that they see no difference in FF resolution without actually comparing FF and APS-C in a valid context. What in the world was rude about that?


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## Jack Douglas (Sep 3, 2014)

Jon, I don't think that was rude unless a person chooses to take it personally based on other issues. When there is disagreement it's challenging to keep everyone happy.

You now have the 5D3 which is resolution-wise pretty similar to me with the 6D and we're both wondering about a 7D2 primarily with respect to its IQ. I'm trying to settle into what really is the truth relative to the reach advantage. It's pretty clear there is no where near a 60% advantage relative to being reach limited and choosing FF or crop, but I'm prepared to believe 20% is realistic. Would you be willing to offer what you consider the various deciding factors that would sway you for or against a 7D2 purchase when it arrives. Let's assume frame rate and AF are acceptible.

Jack


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## jrista (Sep 3, 2014)

Jack Douglas said:


> Jon, I don't think that was rude unless a person chooses to take it personally based on other issues. When there is disagreement it's challenging to keep everyone happy.
> 
> You now have the 5D3 which is resolution-wise pretty similar to me with the 6D and we're both wondering about a 7D2 primarily with respect to its IQ. I'm trying to settle into what really is the truth relative to the reach advantage. It's pretty clear there is no where near a 60% advantage relative to being reach limited and choosing FF or crop, but I'm prepared to believe 20% is realistic. Would you be willing to offer what you consider the various deciding factors that would sway you for or against a 7D2 purchase when it arrives. Let's assume frame rate and AF are acceptible.



People are choosing to take offense at all kinds of stuff lately, and a lot of it seems to come from "sparse" reading of my posts, leading to misinterpretation. I guess that's their prerogative. Seems once you mention DR and put Canon in bad light, everything gets misinterpreted, everyone gets pissy.

As for the 7D II, I'm only really interested in it as a gauge for where Canon is technologically on the sensor front. If it really does only get a very, very modest bump to 20.2mp, no DR improvement, etc. then I really don't have much interest in it in general. I'm not unhappy with the 7D when I need the reach and resolution. I also like the 7D for imaging smaller nebula at a tighter image scale. 

Now, if the 7D II gets something like a 24-26mp sensor, along with a DR improvement, then for me it would at least be a good indicator that Canon has been doing something quietly behind the scenes. That would mean that the next 5D or 1D model should have even more improvements. I still don't think I'd be getting a 7D II. I've got the hang of using the 5D III with the 600/4 and 2x TC now. Both on a tripod and handheld. It ain't good at all for BIF, but it's really nice for when I want to keep a greater distance from birds (which the 7D+600 did pretty well, but with actually fewer pixels on subject.) Because I'm now skilled enough to get pretty nice head shots with the 5DIII/1200mm combo, I don't see as much need for the 7D II personally. With a 24mp or higher resolution sensor, it would offer a nice resolution improvement for astrophotography...however DSLRs, while very easy, REALLY lack the sensitivity and total resolution that a mono CCD with filters offers. So it really wouldn't be all that useful to me for that either. 

So...yeah. The 7D II is pretty much just a milestone marker for Canon sensor tech. They have either done something on that front...or not. DPAF, even if it gets that sensitivity boost their latest DPAF patent describes, just doesn't interest me enough to matter yet. I don't think it's a viable replacement for PDAF, and won't be for a while still. I'm looking to the 7D II to tell me what the 5D IV might be like. I hope it tells me something good.

I seem to be getting a lot of airplane trails in my Elephant Trunk nebula images. I'm not sure what's going on, but it's like an airport outside right now, and I gotta go figure out who is doing what in the airspace right on top of my house...


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## Jack Douglas (Sep 3, 2014)

Thanks Jon, great comments as usual.

Jack


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## Jack Douglas (Sep 3, 2014)

Jon,

"DPAF, even if it gets that sensitivity boost their latest DPAF patent describes, just doesn't interest me enough to matter yet. I don't think it's a viable replacement for PDAF, and won't be for a while still."

I thought the 70D used DPAF in a two pixel phase detect format (PDAF), so could you please clarify. Apparently, the dual pixels covering most of the sensor can function as selectable AF points. What's holding this technology back relative to the anticipated 7D2? It's really hard to believe the 7D2 will actually be a ho hum camera.

Jack


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## ChristopherMarkPerez (Sep 3, 2014)

AlanF said:


> Here is a way of calculating the effective extra reach or resolving power of a crop body versus FF, which will amuse the geeks among us...



MTF is not a measure of resolution, it is a measure of a lenses ability to transmit contrast of the original scene through a lens. That's all it measures.

If what you really want is true image resolution, then there are two correct ways of measuring it. The first is a measurement of the performance of the lens itself. This measurement can be found in using something like a USAF resolution test chart and a microscope to perform aerial inspections of the image of the chart after it has passed through the lens.

Problems with this approach include difficultly in setting up a test bench (it's not easy at all). Additionally, the final result will not include measurements of chromatic aberrations, image distortions, field curvature, etc. The most important missing element in this kind of test is the exclusion of the imaging system itself. However, if the question is about real optical resolution, this test will give you the right answer.

Which leads to the second way of measuring, well, actually calculating real image resolution. This is diagnostic and very simple to perform. Simply take the number of image points ("pixels") in your file, divide by the size of your sensor (in millimeters), and divide by two. This number will represent the number of Line Pair per Millimeter (the measure of the ability to go from one white line to one black line) that your sensor can resolve.

This is rather interesting in that you can quickly see that a Canon 7D 18 mpixel sensor is capable of resolving 116 line pair per mm. The Canon 5D MkII is capable of 78 lppmm. As a comparison, Sony's 36mpixel FF sensor is capable of resolving 102 lppmm and Phase One's monster 80mpixel IQ180 returns 97lppmm.

Taking this a step further, look carefully at the physical limits (as in optical physics) of optical resolution, as measured in lppmm. You see that at f/2, an optically correct lens will return 695lppmm in the center of the scene where the light's wavelength is 589.3mu (green). At f/11, an optically correct lens will return 123lppmm, dropping off to 92lppmm at 25 degrees off-axis tangential.

Looking at this over the years, I have come to realize there is seldom a lens resolving so poorly that a sensor (or old film for that matter) could out-resolve the lens. Sure, there are other important optical effects we need to consider, but we are talking pure resolution here. Nothing more.

Think about this for a moment. MTF does _not_ measure optical resolution. While useful, it does _not_ tell the story of resolution, no matter how much "math" you throw at it. Secondly, and perhaps most interestingly, optical physics show diffraction limited resolution at f/11 EXCEEDS currently manufactured sensors ability to return that resolution in all cases. 

Rather shocking, don't you think?

Back to the original poster's point: Canon's 7D sensor outresolves (using the correct application of the word "resolution") the FF sensors from any manufacturer. It does so, however, for reasons other than those that were brought up.

Correct application of rational thought and real world science can help us properly understand and identify the errors and misleading comments widely published by marketeers and critics of optical imaging systems.


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## PicaPica (Sep 3, 2014)

ChristopherMarkPerez said:


> AlanF said:
> 
> 
> > Here is a way of calculating the effective extra reach or resolving power of a crop body versus FF, which will amuse the geeks among us...
> ...




what about the bayer pattern?

a pixel in the image file is interpolated from photosites on the sensor.
so a bayer pattern sensor has to be worse than what you wrote?


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## Rudeofus (Sep 3, 2014)

PicaPica said:


> what about the bayer pattern?
> 
> a pixel in the image file is interpolated from photosites on the sensor.
> so a bayer pattern sensor has to be worse than what you wrote?



AFAIK the filters on those bayer pixels are quite weak, which means in terms of luminosity you get full resolution plus lots of chroma noise. This bodes well for black/white test charts, but less so for e.g. blue/red test charts. Guess which ones are more common ...


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## ecka (Sep 3, 2014)

ChristopherMarkPerez said:


> AlanF said:
> 
> 
> > Here is a way of calculating the effective extra reach or resolving power of a crop body versus FF, which will amuse the geeks among us...
> ...



You see, if Canon had made a FF camera with 7D's pixel density, then there wouldn't be any questions - FF wins, period.
Nikon did that with their D7000/D7100 vs D800/D810. You crop FF and you get almost exactly what the pre-cropped D7000/D7100 produce. In fact, you can just shoot in DX mode on D800...
So there is no global question about crop winning anything vs FF other than price.
The question is why Canon didn't make that 46mp FF camera?
Was it because consumers didn't ask for it? - Maybe.
Why didn't they ask for it? - Because they are too ignorant in How-It-Works department. They are affected by this ... More_Pixels=More_noise=Bigger_Files=My_Old_iBox_Can't_Handle_it=Crop_Is_Just_As_Good_It's_Just_Magically_Different_Because_Size_Doesn't_Matter=I_Better_Buy_An_Overkill_Lens_For_My_Crop_And_Not_Use_The_Rest_60%_Of_It=I_Don't_Need_That_Much_Pixels_But_Digital_Zoom_Is_Bad#[email protected]*2&$ERROR...System_Reset~Hello_Micro_Four_Thirds=Must_Buy_35-100/2.8_Because_It_Is_70-200/2.8 ... virus .


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## ChristopherMarkPerez (Sep 3, 2014)

PicaPica said:


> ChristopherMarkPerez said:
> 
> 
> > AlanF said:
> ...



You use the image dimensions from the file, not the actual pixels of the sensor. This is why I put "pixels" in quotes. I could have more accurately written "image information node in the output file" or something similar.

The point is, we want the total integration of the information at each "node" of information in the image file, since that's where the real world resolution will live as we process our images.

The calculation gives us the correct answer.

You could also take the slightly harder step of including the four pixels that make up an information node on the sensor itself, but the answer would still be the same in terms of calculating sensor resolution.


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## neuroanatomist (Sep 3, 2014)

ChristopherMarkPerez said:


> The calculation gives us the correct answer.



How does your calculation account for the blurring introduced by the OLPF, or are you suggesting that doesn't affect resolution?


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## ChristopherMarkPerez (Sep 3, 2014)

neuroanatomist said:


> ChristopherMarkPerez said:
> 
> 
> > The calculation gives us the correct answer.
> ...



When you look at the output of your image into a file, in terms of resolution testing, all that matters is that you can go from one file information node to another and transition from pure white to pure black (since that is how the USAF Resolution Test Chart-style tests work).

Indeed, you can observe this yourself by taking a 6:1 contrast ratio scene and look at the white to black transitions at 100 percent on your display. To avoid optical effects, I'd suggest stopping your taking lens to f/5.6 or f/8.

The effect is clear. If your sensor can make the transition from pure white to pure black between two information nodes in your file, your sensor/imaging/electronics system will give you pure resolution per the calculation.

I suspect that manufacturers are quite capable of managing this as every sensor I've ever had in my DSLRs (since the 40D) have behaved as hoped/desired. This is supported by the observations of every lens I've "tested" when attached to camera body. 

I kept seeing the same numbers for USAF-style resolution _from wide open_ all the way down to f/11 and f/16 (for the earlier sensors). The only way to explain it was that the sensor is the limiting factor in terms of pure resolution (again, ignoring other optical effects).


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## ChristopherMarkPerez (Sep 3, 2014)

ecka said:


> You see, if Canon had made a FF camera with 7D's pixel density, then there wouldn't be any questions - FF wins, period.
> Nikon did that with their D7000/D7100 vs D800/D810. You crop FF and you get almost exactly what the pre-cropped D7000/D7100 produce. In fact, you can just shoot in DX mode on D800...
> So there is no global question about crop winning anything vs FF other than price.
> The question is why Canon didn't make that 46mp FF camera?
> ...



I think it's more than that, really.

Think about this from the manufacturer's point of view. The electronics you use to integrate your system cost real money. The Bill Of Materials (BOM) will add up quickly as you select higher performing parts. Over time, the cost of parts will drop (typically) as newer, faster parts become available. 

So it's a balance of price and performance.

From a business perspective, how much Gross Margin do you think you can recover? Answer that with the number of units sold and you'll be well on your way to finding out what the company's quarterly profit will be.

From an electronics point of view, proprietary data-busses (how data moves around inside your camera) are not cheap. Even when you build a system based on existing, open specifications, you still have to source the parts and make sure they will be available over the life of your product (not easy in this day and age). The more mega-pixels you design into your system, the faster your busses need to be to keep the beast from being Dog Slow.

I'm not saying it's not possible. Obviously, if Sony can say they'll release a 50mpixel FF sensor in a couple years, Canon could certainly do it too. But I think the companies are waiting for the BOM costs to drop, mixed with the corporate Gross Margin targets, into the region people will be willing to pay for a new toy.


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## ecka (Sep 3, 2014)

ChristopherMarkPerez said:


> ecka said:
> 
> 
> > You see, if Canon had made a FF camera with 7D's pixel density, then there wouldn't be any questions - FF wins, period.
> ...



Isn't 5D2 the most popular FF DSLR, which was an overpriced MEGApixel monster back in 2008 that forced everyone to buy larger capacity memory cards and new PCs; enjoy FullHD videos they didn't want and struggle shooting sports/action with it's inferior AF system and burst rate because they wanted those beautiful FF images?
All that whining about how much work has to be done and all the investments and new technologies ... is just unreasonable. *We pay for it*. We vote with our money for what we want. There may be 5D Mark 4 coming at Photokina and we can't stop it  and I hope it will have 50+ mega pixels in it  and 4K  and maybe a hybrid viewfinder (OVF+EVF)  and a 4" touch screen  and quad-pixel AF or something  and all that for only $3999 .


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## Jack Douglas (Sep 3, 2014)

Phew, I can barely follow all the technical stuff in these CR threads but what seems to be clear to me is that the economics and market determine an awful lot more than we tend to realize and it's not all about who has the superior technology. Perhaps not unlike a board game with players carefully choosing their moves for fear they will find themselves trapped!

Jack


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## Lee Jay (Sep 3, 2014)

AlanF said:


> Here is a way of calculating the effective extra reach or resolving power of a crop body versus FF, which will amuse the geeks among us.
> 
> Measure the MTF of a lens on the crop (= MTFcrop) and the same lens on the FF (= MTFff). The ratio of the MTFs, MTFcrop/MTFff, gives the relative resolving power of the bodies with that lens. However, the crop body can be placed 1.6x further away to give the same field of view. Therefore, the true effective relative resolving power, R, is given by:
> 
> ...



There are numerous problems with this approach. You're assuming that MTF and resolution are both linear, when neither one is. You're also assuming MTF50 (which is what DPReview reports) is the correct measurement. It's not. Arguments rage, but many people use MTF 9, 5 or even 0 for "resolving power". Third, you're assuming DPReview's measurements are correct when in reality they aren't even self-consistent. I'll provide an example of that last one.

DPReview's measurements using Imatest: http://www.dpreview.com/lensreviews/widget/Fullscreen.ashx?reviews=84&fullscreen=true&av=4&fl=200&vis=VisualiserSharpnessMTF&stack=horizontal&&config=/lensreviews/widget/LensReviewConfiguration.xml%3F4

DxO's measurements using their own tool: http://www.dpreview.com/reviews/lens-compare-fullscreen?compare=false&lensId=canon_70-200_2p8_is_ii&cameraId=canon_eos5dmkii&version=0&fl=200&av=4&view=mtf-ca

At the same setting (200mm and f/4 on 7D), DPReview reports about 1500lp/ph while DxO reports about 1850lp/ph. Perhaps even more interestingly, DPReview reports about 1600 for the 5DII while DxO reports about 2400 for the 5DIII. So, the ratios are 1.6*1500/1600 (1.5) from DPReview for 5DII versus 7D or 1.6*1850/2400 (1.2) from DxO for the 5DIII versus 7D.

So which is it? The differences are very dramatic (1.5 versus 1.2) for cameras with almost exactly the same pixel size.

The facts are these: The actual ratio is always between 1 and the pixel density (PD) ratio, and where it lies in that range is a function of the quality of the technique and of the optics. The better the technique and the better the optics, the higher the number. With the better lenses used well, the actual number is much closer to the PD ratio than it is to 1.

Think of it another way - the PD ratio is like an optically-perfect teleconverter with magnification equal to the PD ratio. Now, real teleconverters aren't optically perfect, but the newer ones are pretty close.

Do teleconverters work when used on full-frame cameras? On the better lenses, yes they do. And so does the PD ratio.


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## jrista (Sep 3, 2014)

Lee Jay said:


> AlanF said:
> 
> 
> > Here is a way of calculating the effective extra reach or resolving power of a crop body versus FF, which will amuse the geeks among us.
> ...



Actually, MTF50 is the standard in optical and photographic measurements. The use of MTF9/10 (Rayleigh) is primarily used to determine the limit of human vision. The use of MTF0 (Dawes) is used to determine contrast at minimum separation...basically, detail is separated so minimally that, in a photographic context, an image of parallel white and black lines would look like pure gray. An image measured at MTF9 would still look almost purely flat gray, and the most dominant source of pixel deviation is going to be noise, rather than detail.

The continued STANDARD use of MTF50 is to ensure that fine detail transmitted by a lens at lower contrast is still resolved. 

There are certain specific use cases where measuring at MTF0 are useful. Under extremely high powered magnification, the bright points of starlight can against the black backdrop of night sky can be fully resolved. A very, very high magnification (and truly excellent seeing or the use lucky imaging over an extended period of time) is required in order for a sensor to actually render the complex Dawes diffraction spots of stars that are not actually fully separated. You also usually need to significantly oversample the stars to get any kind of meaningful result as well.

In a standard photographic context, MTF0 is pretty much meaningless. MTF9 means contrast is so low that noise is going to be the dominant deviation, and therefor is still primarily useless for measuring photographic equipment. Most optical test benches, most reviewers, most mathematical formulas that you can find online, are based on 50% contrast.


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## Lee Jay (Sep 3, 2014)

jrista said:


> Actually, MTF50 is the standard in optical and photographic measurements. The use of MTF9/10 (Rayleigh) is primarily used to determine the limit of human vision.



Or, say, telescope resolving power. This discussion is about resolving power, and MTF50 is way too low for that.



> The use of MTF0 (Dawes) is used to determine contrast at minimum separation...basically, detail is separated so minimally that, in a photographic context, an image of parallel white and black lines would look like pure gray. An image measured at MTF9 would still look almost purely flat gray, and the most dominant source of pixel deviation is going to be noise, rather than detail.
> 
> The continued STANDARD use of MTF50 is to ensure that fine detail transmitted by a lens at lower contrast is still resolved.



I disagree. MTF50 is used to represent the lower limit of "pixel sharp". The catch is, you don't want "pixel sharp". If your images are sharp at the pixel level, then you are undersampling your optics, and therefore throwing away detail.



> In a standard photographic context, MTF0 is pretty much meaningless.



I agree.



> MTF9 means contrast is so low that noise is going to be the dominant deviation, and therefor is still primarily useless for measuring photographic equipment.



I disagree. In fact, I've shot and extracted detail below MTF5. Of course, how far you can go here depends greatly on the noise in the image. That's why stacking allows you to pull out much more detail than you can without stacking - the effective exposure is dramatically longer and therefore the noise is dramatically smaller.

At lower ISOs, MTF9 is perfectly reasonable as a rough limit on resolving power. You only really need MTF50 when you are at extremely noisy exposures or, when you want "pixel sharp" as your target which, as I said above, you shouldn't.


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## jrista (Sep 3, 2014)

Lee Jay said:


> > MTF9 means contrast is so low that noise is going to be the dominant deviation, and therefor is still primarily useless for measuring photographic equipment.
> 
> 
> 
> ...



I'm guessing your MTF5 images were in an astrophotography context? When it comes to astrophotography, I agree. But, I also think that is a pretty radically different field than regular photography. With AP, we have a whole lot more options and means of reducing noise, which makes resolving ultra low contrast detail (say, the surface of the moon, or cloud band detail in Jupiter) vastly more viable.

When it comes to "terrestrial" photography, I think there are still too many things working against the ability of camera systems to meaningfully resolve detail that MTF9 is more likely to result in the question: "Is that noise or detail?" than it actually results in a meaningful result. There may be a few occasions where you can resort to stacking for terrestrial photography as well...still scenes for example, maybe landscapes in certain circumstances. But for the most part, I'd say such low contrast scenarios are more viable for very niche types of photography...namely astrophotography. 

I myself have probably resolved detail around MTF9. I use lucky imaging to image the moon, and I've tried Jupiter a few times. I simply don't have the focal length required...for my sensor pixel sizes, I need somewhere between 8,000mm and 10,000mm...and ultimately, resolving power in a telescope is related to the diameter of the aperture...so were talking about a 12-14" telescope with a 3x to 5x barlow.  THEN, yeah, then were really talking about proper oversampling and some major resolving power of very low contrast detail. (Plus, the way we process such data, were not talking about a single frame...it's usually hundreds or thousands of frames integrated together using Sigma-clipping and superresolution algorithms.)


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## Andyx01 (Sep 3, 2014)

ecka said:


> ChristopherMarkPerez said:
> 
> 
> > AlanF said:
> ...



Lmao, +1

You forgot the part about how the equipment doesn't matter, and a good photographer could take a photo better than the hubble deep field with their iPhone.


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## Lee Jay (Sep 3, 2014)

I'm not saying MTF5 is ordinarily achievable with regular photography. I'm saying that, or maybe MTF9 should be used as "extinction". MTF50 is so far below extinction that's it's not even close. If that were the case, anything below MTF 0.5 on the lens charts would be so blurry that it might as well be unrecognizable at the pixel level, and that simply isn't the case. Look at the 16-35II, for example. Something like half of the MTF chart is below 0.5 (MTF 50) at 30lp/mm!

http://www.usa.canon.com/cusa/consumer/products/cameras/ef_lens_lineup/ef_16_35mm_f_2_8l_ii_usm


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## Lee Jay (Sep 3, 2014)

Here's what Imatest says: http://www.imatest.com/docs/sharpness/

"MTF50 or MTF50P are good parameters for comparing the sharpness of different cameras and lenses for two reasons: (1) Image contrast is half its low frequency or peak values,hence detail is still quite visible. The eye is relatively insensitive to detail at spatial frequencies where MTF is low: 10% or less."

I agree, fully, with that. MTF50 is about "sharp" ("detail is still quite visible") while MTF10 or so is about "extinction" (the limit of resolving power). I use MTF5 for stacked astro videos, and 10 for regular low-ISO (say, 400 or less, give or take, on SLRs) photography.


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## jrista (Sep 3, 2014)

Yeah, I agree with that, MTF50 for sharpness, MTF10 for extinction. When it comes to testing lenses, though, and I think still viable for performing simple relative comparisons like Alan is doing, MTF50 is fine. Not only that, it is VERY easy to get lens test results in MTF50...it is significantly more difficult to find them performed at lower contrast levels.

Alan's little calculation is just a basic means of relatively comparing cameras with lenses on them, that's all. And I think it works well for that.


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## Lee Jay (Sep 3, 2014)

jrista said:


> Yeah, I agree with that, MTF50 for sharpness, MTF10 for extinction. When it comes to testing lenses, though, and I think still viable for performing simple relative comparisons like Alan is doing, MTF50 is fine. Not only that, it is VERY easy to get lens test results in MTF50...it is significantly more difficult to find them performed at lower contrast levels.
> 
> Alan's little calculation is just a basic means of relatively comparing cameras with lenses on them, that's all. And I think it works well for that.



It's almost impossible to get lens test results of any sort, including MTF50. We only have system tests, and those include the AA filter.

As I showed, even Alan's calculation is self-inconsistent, at least when comparing DPReview data to DPReview's reporting of DxO data.


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## jrista (Sep 3, 2014)

Lee Jay said:


> jrista said:
> 
> 
> > Yeah, I agree with that, MTF50 for sharpness, MTF10 for extinction. When it comes to testing lenses, though, and I think still viable for performing simple relative comparisons like Alan is doing, MTF50 is fine. Not only that, it is VERY easy to get lens test results in MTF50...it is significantly more difficult to find them performed at lower contrast levels.
> ...



I think your overcomplicating things. Pick a source, any *single *source, for lens data. DPR is fine. Then, compare any two systems using only that data. That's all that's necessary. Alan's formula is only for simple comparisons. It isn't intended to be highly accurate, just accurate enough to demonstrate what you should generally be expecting, performance wise, in real life. So long as your data source for lens (or lens+sensor, as they really are) tests is consistent, whether DPR's data matches DXO data or anyone elses data doesn't matter.


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## Lee Jay (Sep 3, 2014)

jrista said:


> Lee Jay said:
> 
> 
> > jrista said:
> ...



Even though one got 1.2x and one got 1.5x with basically the same pixel sizes? That's a pretty enormous range when 1.0-1.5 is what one would get without any data at all and just assuming either a horrible lens (1.0) or a "perfect" lens (1.5).


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## jrista (Sep 3, 2014)

Lee Jay said:


> jrista said:
> 
> 
> > Lee Jay said:
> ...



Pixel size alone is not the sole factor in determining sharpness and microcontrast. AA filter, as you said yourself, plays a role, among other things. You can resort to manufacturer mathematically generated MTF charts if you want a more consistent source of data. Those charts tell you a wealth of information...but you don't have to use it all. You can choose to use the f/8 or max aperture data, and you can pick a range from center to corner for your data points.


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## Lee Jay (Sep 3, 2014)

jrista said:


> Pixel size alone is not the sole factor in determining sharpness and microcontrast. AA filter, as you said yourself, plays a role, among other things. You can resort to manufacturer mathematically generated MTF charts if you want a more consistent source of data. Those charts tell you a wealth of information...but you don't have to use it all. You can choose to use the f/8 or max aperture data, and you can pick a range from center to corner for your data points.



Yeah, but the 5DIII is nowhere close to this much better than the 5DII as far as resolution goes.

Canon's calculated MTF charts are a major problem since they don't include diffraction. You'd have to adjust all of Canon's data to include that, somehow, and it's not even clear how exactly they exclude it.


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## AlanF (Sep 3, 2014)

Stu_bert said:


> AlanF said:
> 
> 
> > Northstar said:
> ...



Stu
Sorry I missed this question - I am busy in Paris. If the subject is a long distance from the lens then the image is very close to being the focal length away from the lens. So, 

subject distance/focal length = subject size/image size.


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## DominoDude (Sep 4, 2014)

AlanF said:


> Stu_bert said:
> 
> 
> > AlanF said:
> ...



Here's what I've done. I have listed all my lenses with their corresponding FOV's (in degrees, but for the formula I need to work with half the FOV and with the units in radians) for both APS-C and FF in a spreadsheet. I then have the size of the subject (in meters), and a field for how much "air" I want around my subject (in my case I want like 25% free space around).

Example answering: At what distance will I fill the frame?

```
Length of subject (L) = 1m --> L+Air% = 1,25m
```
Chosen lens is a 400mm on a FF body.

```
FOV(400mm) = 6,17°. I need FOV(400mm)/2 and to turn that into rads --> 0,054
```
To calculate the distance (D, in meters) I use

```
D = (L+Air%) * cot(FOV(400)/2) /2
 D = (1,25 * cot(0,054)) /2
 D = 11,6m
```

I can't make this look as good as I intended in post, but I hope it makes some sense, and that it can be turned into a formula you can use.


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## ecka (Sep 4, 2014)

Andyx01 said:


> ecka said:
> 
> 
> > ChristopherMarkPerez said:
> ...



Thanks for reminding about that one. Actually, there are plenty of them (like - "macro lenses are too sharp for portraits" or "I shoot JPEG, because I'm no pixel-peeper" or "look at these 300x200 images, 1DX and a Rebel both look the same, so why pay more..."), but who's counting


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## martinslade (Sep 21, 2014)

Can anyone tell me why the same lens on a crop vs FF body show different sharpness as measured by DXO and seen on the-digital-picture lens quality tool... thanks..?

http://www.dxomark.com/Lenses/Canon/Canon-EF70-200mm-f28L-IS-II-USM-mounted-on-Canon-EOS-5D-Mark-III__795

http://www.dxomark.com/Lenses/Canon/Canon-EF70-200mm-f28L-IS-II-USM-mounted-on-Canon-EOS-7D__619

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=687&Camera=453&Sample=0&FLI=1&API=0&LensComp=687&CameraComp=736&SampleComp=0&FLIComp=1&APIComp=0


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## ecka (Sep 21, 2014)

martinslade said:


> Can anyone tell me why the same lens on a crop vs FF body show different sharpness as measured by DXO and seen on the-digital-picture lens quality tool... thanks..?
> 
> http://www.dxomark.com/Lenses/Canon/Canon-EF70-200mm-f28L-IS-II-USM-mounted-on-Canon-EOS-5D-Mark-III__795
> 
> ...



Because on crop you are using only 40% of the glass to get the same picture, which leads to lower sharpness and contrast as well as stronger aberrations (because you are putting more pixels there).


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## martinslade (Sep 22, 2014)

Thanks ecka for your reply. I must admit I don't really get it. What I don't understand is that a given lens produces an in focus image circle and either a crop or FF sensor is "placed" in that circle, albeit with different numbers/size of pixels and the 2 images are very different. The fact that the 2 sensors are a different size appears irrelevant. The FF will cover more of the image circle than the crop sensor.

Can anyone give me a structured/scientific explanation as to what's happening please... thanks...



ecka said:


> martinslade said:
> 
> 
> > Can anyone tell me why the same lens on a crop vs FF body show different sharpness as measured by DXO and seen on the-digital-picture lens quality tool... thanks..?
> ...


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## martinslade (Sep 22, 2014)

Thanks ecka for your reply. I must admit I don't really get it. What I don't understand is that a given lens produces an in focus image circle and either a crop or FF sensor is "placed" in that circle, albeit with different numbers/size of pixels and the 2 images are very different. The fact that the 2 sensors are a different size appears irrelevant. The FF will cover more of the image circle than the crop sensor.

Can anyone give me a structured/scientific explanation as to what's happening please... thanks...


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## Lee Jay (Sep 22, 2014)

martinslade said:


> Thanks ecka for your reply. I must admit I don't really get it. What I don't understand is that a given lens produces an in focus image circle and either a crop or FF sensor is "placed" in that circle, albeit with different numbers/size of pixels and the 2 images are very different. The fact that the 2 sensors are a different size appears irrelevant. The FF will cover more of the image circle than the crop sensor.
> 
> Can anyone give me a structured/scientific explanation as to what's happening please... thanks...



The smaller sensor requires greater enlargement for the same final image size. This means the original must be much sharper for the same final sharpness.

Looked at another way, if you measure lens resolving power in line pairs per picture height, the smaller picture height means less resolving power when you have less picture height.


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## ecka (Sep 22, 2014)

martinslade said:


> Thanks ecka for your reply. I must admit I don't really get it. What I don't understand is that a given lens produces an in focus image circle and either a crop or FF sensor is "placed" in that circle, albeit with different numbers/size of pixels and the 2 images are very different. The fact that the 2 sensors are a different size appears irrelevant. The FF will cover more of the image circle than the crop sensor.
> 
> Can anyone give me a structured/scientific explanation as to what's happening please... thanks...



If you can't understand a simple explanation, what makes you think that you will understand the scientific one? Or then you'll just take it on faith, because some book knows better? I'm sorry, I don't get your logic .

First, you must understand how optics work, I mean physics. Every optical system is diffraction-limited (which means there is a limited maximum resolution it is able to project) and you can't just put whatever number of pixels you want (or imagine) and still get a perfectly sharp image. Sensor size is very relevant. Read a book .


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## Sporgon (Sep 22, 2014)

martinslade said:


> Thanks ecka for your reply. I must admit I don't really get it. What I don't understand is that a given lens produces an in focus image circle and either a crop or FF sensor is "placed" in that circle, albeit with different numbers/size of pixels and the 2 images are very different. The fact that the 2 sensors are a different size appears irrelevant. The FF will cover more of the image circle than the crop sensor.
> 
> Can anyone give me a structured/scientific explanation as to what's happening please... thanks...



Basically the smaller the sensor ( or film ) format, the smaller the magnification at capture ( shorter focal length lens, smaller format) and the greater the magnification required to view = loss of quality.


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## martinslade (Sep 22, 2014)

Penny hath dropped... think I have been over analysing and forgotten the obvious... doh...

Thanks for all your help/comments


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## J.R. (Sep 22, 2014)

I hope I'm not high jacking this thread ... It's gone way too scientific for me to comprehend fully despite trawling tHrough the posts. 

Would it be a reasonable conclusion to draw that at low ISO (100-400), the difference between the APS-C and the FF is negligible, thereby meaning that the reach benefit could be satisfactorily obtained at the low ISOs?


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## ecka (Sep 23, 2014)

J.R. said:


> I hope I'm not high jacking this thread ... It's gone way too scientific for me to comprehend fully despite trawling tHrough the posts.
> 
> Would it be a reasonable conclusion to draw that at low ISO (100-400), the difference between the APS-C and the FF is negligible, thereby meaning that the reach benefit could be satisfactorily obtained at the low ISOs?



There is always a difference. It may only be negligible for those who don't care.


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## J.R. (Sep 23, 2014)

ecka said:


> J.R. said:
> 
> 
> > I hope I'm not high jacking this thread ... It's gone way too scientific for me to comprehend fully despite trawling tHrough the posts.
> ...



Thanks. What differences would be obvious and what would be the ones you would look for? Again, I'm talking only of low ISO.


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## ecka (Sep 23, 2014)

J.R. said:


> ecka said:
> 
> 
> > J.R. said:
> ...



Sharpness, contrast, aberrations.


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## J.R. (Sep 23, 2014)

ecka said:


> J.R. said:
> 
> 
> > ecka said:
> ...



Hmm ... so basically sharpness and contrast are the obvious ones and the aberrations would be the one you would look for. Thanks for this. 

To my mind sharpness has been relative, depending more on the available light and the focusing. Why the FF should be sharper is something I've not really understood. 

BTW, wouldn't the aberrations be caused by the lens instead of the camera body?


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## ecka (Sep 23, 2014)

J.R. said:


> ecka said:
> 
> 
> > J.R. said:
> ...



(Hint) Diffraction-limited optics = FF sharper, either because the pixels are larger or there is more of them.
Aberrations are caused by the lens. If a lens is producing (let's say) 3 pixel wide aberration on 20mp FF sensor, then the same lens will produce 5 pixels wide aberration on 20mp APS-C sensor just because those pixels are 1.6x smaller and denser. Simple math here.


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## J.R. (Sep 23, 2014)

ecka said:


> Aberrations are caused by the lens. If a lens is producing (let's say) 3 pixel wide aberration on 20mp FF sensor, then the same lens will produce 5 pixels wide aberration on 20mp APS-C sensor just because those pixels are 1.6x smaller and denser. Simple math here.



Thanks


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## weixing (Sep 23, 2014)

ecka said:


> J.R. said:
> 
> 
> > ecka said:
> ...


Hi,
IMHO, it's not a straight forward answer... yes, a crop sensor will "amplify" the lens aberrations, but if you are using a FF lens on a crop sensor especially a good FF lens, you might get better IQ as the lens usually perform better at the center area... Look at any MTF lens and you'll see a lot of lens start to degrade after the 15mm mark, but a crop sensor user can basically ignore anything after the 10mm on the MTF chart.

Have a nice day.


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## ecka (Sep 23, 2014)

weixing said:


> ecka said:
> 
> 
> > J.R. said:
> ...



No, not really. Imagine that you have ~50mp FF sensor and ~20mp APS-C sensor. Both would produce the same level of IQ, only FF gives you 2.5 times more of it + you can crop it to get exactly same thing. Using smaller sensor for a lens with soft corners is a lousy excuse. Theoretically, we can take each lens element and cut it down to APS-C image circle requirements and it wouldn't be the perfect formula. It would have unnecessarily thick glass. The secret lies in proportions. You can visualize the FF lens image quality as a 3D graph in a shape of a cone. Now if you cut it down to an APS-C size, you still get a cone. This way you may get rid of the problematic corners, but the sharpest part of it (the middle) won't be as sharp as FF. It's a compromise and a big one.


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## krisbell (Sep 23, 2014)

Total simpleton here that has tried gamely to follow the logic of this thread. I accept the circa 20% difference but can someone put this in laymans terms for me....I currently have a 5DIII with 300mm and 2x converter. However, with a 7D2 I could achieve slightly greater 'reach' with a 1.4x - in this instance would a 7D2 with 300mm and 1.4x be a better option than a 5dIII with 300mm and 2x converter? I am reach limited more often than not and I guess the other benefits of the 7D setup include higher FPS, lighter weight and faster aperture.


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## privatebydesign (Sep 23, 2014)

krisbell said:


> Total simpleton here that has tried gamely to follow the logic of this thread. I accept the circa 20% difference but can someone put this in laymans terms for me....I currently have a 5DIII with 300mm and 2x converter. However, with a 7D2 I could achieve slightly greater 'reach' with a 1.4x - in this instance would a 7D2 with 300mm and 1.4x be a better option than a 5dIII with 300mm and 2x converter? I am reach limited more often than not and I guess the other benefits of the 7D setup include higher FPS, lighter weight and faster aperture.




Hi krisbell,

Without knowing what 300 and TC's it is difficult to give an accurate answer. In general though the crop camera advantages are not in the "pixel on duck" meme, they are, as you say, framerate, viewfinder view, size, weight, cost etc etc.


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## krisbell (Sep 23, 2014)

Thanks for the reply, though if its the same lens being switched between the two systems I'm not sure why it would matter - though this could be my ignorance shining through (again!). For what its worth I have a 300mm f2.8 II and 2xIII(as per my signature). I'm thinking that with the significantly less damage a 1.4x has on image quality, combined with a faster aperture, as well as weight savings, FPS and reach may make the 7DII a significantly better option than the 5DIII.


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## privatebydesign (Sep 23, 2014)

The 300mm f2.8 II and 2xIII is just about the only combination I would say maintains enough IQ for it to be a wash IQ wise. I'd recommend you make a purchase decision not on "reach capabilities, though the 7D MkII and 300mm f2.8 II and 2xIII should be very good, but on the other differences already mentioned, framerate, viewfinder view, size, weight, cost etc etc.


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## krisbell (Sep 23, 2014)

Thanks privatebydesign - I was actually effectively eliminating reach by pairing the 7DII with a 1.4x (rather than a 2x on the 5DIII) though this would still give me 70mm more on the 7D. In this instance is it possible IQ may be comparable between 5DIII+300II+2xIII vs 7DII+300II+1.4xIII?


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## ecka (Sep 23, 2014)

krisbell said:


> Thanks privatebydesign - I was actually effectively eliminating reach by pairing the 7DII with a 1.4x (rather than a 2x on the 5DIII) though this would still give me 70mm more on the 7D. In this instance is it possible IQ may be comparable between 5DIII+300II+2xIII vs 7DII+300II+1.4xIII?



That's an interesting question. There was a similar debate ("FF vs crop", maybe 4 or 5 years ago, can't remember the source right now) in which some people demonstrated 5D2+1.4x+tele.lens being as good or better than 7D+tele.lens.


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## privatebydesign (Sep 23, 2014)

krisbell said:


> Thanks privatebydesign - I was actually effectively eliminating reach by pairing the 7DII with a 1.4x (rather than a 2x on the 5DIII) though this would still give me 70mm more on the 7D. In this instance is it possible IQ may be comparable between 5DIII+300II+2xIII vs 7DII+300II+1.4xIII?



I would say the differences will be so nuanced in that specific scenario anybody stating one over the other would only be guessing, especially as there aren't any 7D MkII's out there in retail customers hands yet.

When I investigated the same question for the 7D and 1Ds MkIII era cameras and 300 f2.8 IS MkI, I tested them and concluded the 7D didn't give me anything extra so didn't buy one. But this latest iteration of the question will need to be tested by you for your personal use and opinion. What killed my interest in the 7D was the comparative noise, even at base iso, but for others that wasn't as important.

I'd suggest renting and testing when they are available, or buy from somebody with a very generous return policy to give you the opportunity to draw your own conclusions.


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## AlanF (Sep 23, 2014)

krisbell said:


> Total simpleton here that has tried gamely to follow the logic of this thread. I accept the circa 20% difference but can someone put this in laymans terms for me....I currently have a 5DIII with 300mm and 2x converter. However, with a 7D2 I could achieve slightly greater 'reach' with a 1.4x - in this instance would a 7D2 with 300mm and 1.4x be a better option than a 5dIII with 300mm and 2x converter? I am reach limited more often than not and I guess the other benefits of the 7D setup include higher FPS, lighter weight and faster aperture.



I've done the comparison 70D + 300mm f/2.8 II+ 1.4xTC III f/4 vs 5DIII + 300mm f/2.8 II + 2xTC III f/5.6.

There is little to choose between them, if anything the 70D was sharper. The extra stop compensates for the extra noise on the 70D - I used iso 640 for the 70D and 1250 on the 5DIII, and the 300mmx1.4 TC combination has a slight inherent IQ edge over the 300x2TC. So, I think the 7DII with the f/2.8 II+ 1.4xTC III or the new 400mm f/4 DO would be a very nice set up. 

Thanks for getting me to look at my old images (I had deleted them from Dropbox and had to recover them). It's made me change my mind about getting a 7DII as for the particular case of the 300mm f/2.8 the crop looks as if it will outperform the 5DIII.


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## krisbell (Sep 24, 2014)

Thanks for the replies all, and AlanF that is a really useful comparison. Seems like a no-brainer if the 7DII will actually match or outperform the IQ of the 5DIII in this (admittedly very specific) scenario - plus the weight, FPS advantages etc


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## FEBS (Sep 24, 2014)

krisbell said:


> Thanks for the replies all, and AlanF that is a really useful comparison. Seems like a no-brainer if the 7DII will actually match or outperform the IQ of the 5DIII in this (admittedly very specific) scenario - plus the weight, FPS advantages etc



I don't know the weight of the 7D2, but the difference between the 7D and 5D3 when compared with a lens like 300 2.8 on top is not significant. The longer extender (2x instead of 1.4x) might however bring the weight of the lens a little further away from the way, so the torque needed to keep the 5D3 straight is higher would be higher. But from point of weight, there is almost no difference.


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## FEBS (Sep 24, 2014)

AlanF said:


> krisbell said:
> 
> 
> > Total simpleton here that has tried gamely to follow the logic of this thread. I accept the circa 20% difference but can someone put this in laymans terms for me....I currently have a 5DIII with 300mm and 2x converter. However, with a 7D2 I could achieve slightly greater 'reach' with a 1.4x - in this instance would a 7D2 with 300mm and 1.4x be a better option than a 5dIII with 300mm and 2x converter? I am reach limited more often than not and I guess the other benefits of the 7D setup include higher FPS, lighter weight and faster aperture.
> ...



Alan, the reason I don't use my 7D anymore is mostly caused by the difference in AF (compared to 5D3 or 1Dx) and the noise, even at low iso levels. I know, as one of my friends has one, that the 70D is much better for noise then the 7D. As I was not really impressed by the AF of the 70D (missing focus point expansion), I waited on the release of the 7D2. I did take nice photo's with the 7D and 300/2.8. However AF and noise didn't make me feel comfortable to keep the 7D as a backup camera. With the specification of the new released 7D2, even if the sensor performs equal to the 70D, I think I will have soon a rock solid backup camera. I'm fully confident that the 7D2 with the 300/2.8 will create mindblowing pictures. I'm happy to see you confirm the same idea about 70D/7D2 with a lens like 300/2.8.


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## krisbell (Sep 24, 2014)

FEBS said:


> krisbell said:
> 
> 
> > Thanks for the replies all, and AlanF that is a really useful comparison. Seems like a no-brainer if the 7DII will actually match or outperform the IQ of the 5DIII in this (admittedly very specific) scenario - plus the weight, FPS advantages etc
> ...



Febs - its not just the weight when handholding to take a picture, but I carry my 5DIII+300II+2xIII for miles and miles through jungles in stifling heat where my neck/shoulders would be grateful for even a 300g reduction in weight. I agree its not a major consideration but all these little things add up to make it a very viable alternative to a 5DIII for my long telephoto work.


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## FEBS (Sep 24, 2014)

krisbell said:


> FEBS said:
> 
> 
> > krisbell said:
> ...



But if it is really the weight for walking around then you will not feel the difference. as the weight of a 7D2+1.4x+300/2.8 compared to 5D3+2.0x+300/2.8 will be something about 200gr. The only advice I can give you for that is NOT to use the standard strap. I have now problem for walking around a whole day with a 5D3 with 70-200/2.8 and a 1Dx with 200-400/4 or 300/2.8+2.0x. I use double strap from black rapid, and at the end of the day you will feel nothing there about. But the standard strap of Canon, I will feel my neck within a few hours even with the 7D+70-200/2.8.


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## ecka (Sep 24, 2014)

Look what I found 

http://www.juzaphoto.com/article.php?l=en&article=75


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## krisbell (Sep 24, 2014)

Thanks for the link Ecka - exactly the sort of thing I was looking for. Based on this I'm guessing the IQ difference between 5DIII+2x and 7DII+1.4x will be pretty minimal.


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## SPKoko (Sep 24, 2014)

The OP compares a 50D with a 5DII using data from Photozone. He also compares a 7D with a 5DIII using data from dpreview. In both cases, the crop sensor has a lower number of MP.

Why not compare a 70D with a 6D, both having the same number of MP, using data from DxOMark? When comparing a 70D and a 6D with a 300mm f2.8 II @ f5.6, we see that the maximum accutance of the 70D is 72.3 and the maximum accutance of the 6D is 76.1. That is, using the 70D we have 95% of the resolution and 1.6 more reach. I bet that the 1.4x and 2x teleconverters lose more resolution than that and anyway they can be used with crop bodies too!

If the glass is good enough and we are reach limited, there seems to be a clear advantage in crop sensors.


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## AlanF (Sep 24, 2014)

Here's the test, my favourite medieval chimney, ca. 900x700 100% crops side by side. Left is the 70D, 420mm at f/4 iso640, right is 5DIII, 600mm f/5.6 iso1250. Identical processing of both. 

The 7D was not as good as the 70D in my hands. If you look at the 60D @420mm with the 300mm/2.8 vs 5DIII at 600 mm; and then compensate for the poorer performance of the 60D by comparing the 70D with the 60 on the 200mm f/2 on the TDP site, it looks as if the 70D and hence the 7DII are as good as the 5DIII in general in this comparison.

By the way FEBS, I am the treasurer of FEBS so watch your bank account!


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## NancyP (Sep 24, 2014)

More pixels on the bird. That is what I get with crop camera. Pixel density. If I were shooting stuffed birds I would use full frame and the 180 mm macro lens. In real life, it is hard to get enough pixels on the bird.


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## ecka (Sep 24, 2014)

NancyP said:


> More pixels on the bird. That is what I get with crop camera. Pixel density. If I were shooting stuffed birds I would use full frame and the 180 mm macro lens. In real life, it is hard to get enough pixels on the bird.



Hmm, at these prices it is cheaper to buy the bird ).


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## Deleted member 91053 (Sep 24, 2014)

NancyP said:


> More pixels on the bird. That is what I get with crop camera. Pixel density. If I were shooting stuffed birds I would use full frame and the 180 mm macro lens. In real life, it is hard to get enough pixels on the bird.



Curious- I have gone the opposite route!
My main subjects are small birds and I have achieved better results when I moved to larger sensors (Apsc to Apsh to FF). True the cameras have improved in areas other than sensor size but the pixel density has dropped significantly - yet I achieve better results, not to mention the silly ISO levels that I can now use. My 18mp FF sensor is looking sparsely populated compared to the current rash of high MP sensors but, in all the comparisons that I yet have tried, produces better results for me.


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## FEBS (Sep 25, 2014)

AlanF said:


> By the way FEBS, I am the treasurer of FEBS so watch your bank account!



Oh, it was you that did somewhere make a remark about the word FEBS. I forgot what it meant for you but for me it's indeed an abbreviation, but from Francois, Elly, Bart & Sarah., So all the members of our family.

Francois


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## Valvebounce (Sep 25, 2014)

Hi FEBS. 
I have to say that this was one of the best things I did, bought a Black Rapid Double! I carried a Gripped 40D with a Sigma 150-500 and a Gripped 7D with 70-200 2.8 II with 2x III all day, felt no ill effect AT ALL, compared to carrying just the Un gripped 7D with 17-70 for part of a day giving me neck ache and subsequently a head ache! 
I also bought an OpTech pro strap, the spongy springy one, I have yet to try that one in anger, but it is shaped to keep the strap down off the neck a bit, and is springy to help reduce the perceived weight of the gear. 
Definitely ditch the original strap for long shoots carrying a camera! 

Cheers, Graham. 



FEBS said:


> But if it is really the weight for walking around then you will not feel the difference. as the weight of a 7D2+1.4x+300/2.8 compared to 5D3+2.0x+300/2.8 will be something about 200gr. The only advice I can give you for that is NOT to use the standard strap. I have now problem for walking around a whole day with a 5D3 with 70-200/2.8 and a 1Dx with 200-400/4 or 300/2.8+2.0x. I use double strap from black rapid, and at the end of the day you will feel nothing there about. But the standard strap of Canon, I will feel my neck within a few hours even with the 7D+70-200/2.8.


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## AlanF (Sep 28, 2014)

Yesterday, I tried out the 70D with the 300/2.8 II + 1.4xTC III. It was good at f/4. But, for reach limited subjects, the 300/2.8 II + 2xTC III was even better.

An interesting point I read on TDP from a conversation with Chuck Westfull. You read regularly that the 1.4xTC III slows down focussing speed by 50% and the 2x by 75%, but in practice they do not. Addition of a TC actually speeds up focussing because the glass has to be moved through shorter distances and so the 50% and 75% reductions are there to bring them back to the speed of the bare lens.


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## skoobey (Sep 28, 2014)

Has nothing to do with resolving power, both of them have great resolving power, it's about two things:

Working distance. Crop has more reach, FF can be used to get super wide shots in tiny spaces.

Depth of field. At same composition, same lens, same settings, FF will give you shallower depth of field. Why? Because you're much closer to the subject.


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## SPKoko (Sep 28, 2014)

AlanF said:


> Yesterday, I tried out the 70D with the 300/2.8 II + 1.4xTC III. It was good at f/4. But, for reach limited subjects, the 300/2.8 II + 2xTC III was even better.



Do you mean that the 2xTC on FF is better than a 70D+1.4xTC? And what about a 70D vs 1.4xTC on FF?


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## AlanF (Sep 29, 2014)

SPKoko said:


> AlanF said:
> 
> 
> > Yesterday, I tried out the 70D with the 300/2.8 II + 1.4xTC III. It was good at f/4. But, for reach limited subjects, the 300/2.8 II + 2xTC III was even better.
> ...



I posted earlier an example where 70D with the 300/2.8 II + 1.4xTC III was as good as 5DIII with the 300/2.8 II + 2xTC III. I meant here that 70D with the 300/2.8 II + 2xTC III was better than 70D with the 300/2.8 II + 1.4xTC III in a highly reach limited situation.

I haven't compared 70D plus 300/2.8 II vs 5DIII with the 300/2.8 II + 1.4xTC III.


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