# Image IQ



## chauncey (Sep 2, 2016)

I do a fair amount of macro work...if image size is of less importance than is acute image sharpness, 
would I see a more acutely sharp IQ @ 300% by using a lower MP sensor (older) as opposed to one 
of the newer 30-50 MP beasts? 

Am heavy into PS CC.


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## Mt Spokane Photography (Sep 2, 2016)

You can boost one of your images to 300% to see if you think its sharper. If so, go for it.

Most of us see images as being sharper when viewed at less than 100%, and at 300% they look awful.

I'm not even sure where your 300% number came from or what its significance might be.


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## chauncey (Sep 2, 2016)

What difference does it make where I got it?


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## arbitrage (Sep 2, 2016)

The 5DSR will likely look best at 300% if you take care to control your shooting so that you maximize its potential resolving power.

For wildlife with long lenses I've found that without great technique a 20MP 1DX image viewed at 200% will look as good as the 5DSR at 100%. However, with very good technique the 5DSR will show its advantage.


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## awinphoto (Sep 2, 2016)

There are only really 3 things that control DOF of the image. The physical size of the sensor/film, the aperture settings, and the distance of the lens to the subject. So that being said, a 5d will have shallower DOF in relations to a crop sensor because the crop sensor has a smaller capture area. Doesn't matter if you have a 6MP 10D or a 15MP 50D... the sensor size is physically the same. Now cameras, depending on the MP and the lenses used, have a sweet spot as far as optimum focus... The more MP you have, the shallower DOF to get that sweet spot... such as around F5.6 for the 50D... Of course, on macro, that would still be very shallow, but it's a tradeoff. So the question would be are you looking for the most DOF, or sharp sharp images.... the sharpest images likely wont have the most DOF but that's something you will have to determine.


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## neuroanatomist (Sep 2, 2016)

awinphoto said:


> There are only really 3 things that control DOF of the image. The physical size of the sensor/film, the aperture settings, and the distance of the lens to the subject.



Not quite. If that were true, I could focus on a subject 6 m away with my 1D X and lens set to f/4, and get the same DoF if that lens was my 11-24L or my 600/4L...and that is simply not true. Rather, the three things that control depth of field are sensor size, aperture, and *magnification* (and magnification is determined by subject distance and focal length of lens).


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## awinphoto (Sep 2, 2016)

neuroanatomist said:


> awinphoto said:
> 
> 
> > There are only really 3 things that control DOF of the image. The physical size of the sensor/film, the aperture settings, and the distance of the lens to the subject.
> ...



nuero... those 3 elements work together... So by focusing on a subject 6m away, your thereby minimizing the effect of the f4... If you take any 1 of these elements by themselves... a 4x5 film will have shallower DOF than a 35mm... F2.8 will have shallower DOF than F22... focusing at the min focus distance will have a shallower DOF than focusing at infinity... these are set parameters.... now if you mesh them together, like any photographer does, focusing with a 4x5 camera at minimum focus distance at 2.8 will yield shallower DOF than any other camera short of a larger filmed back, such as an 8x10 or bigger. If you use these 3 principles together, then you can effectively determine and guage total DOF. NOW, as to your example of a 600mm F4 vs a 11-24L at the same setting, everything being the same sensor, the comparison really is unfair as the minimum focus distance will be different in comparison to each other. If possible, if you take the lenses, shoot them at the same min focus distance, and either zoom in or zoom out each image so you see roughly the same crop area, you will have very similar if not identical DOF... it's just easier to see zoomed in and isolated. Any differences I would think would be due to distortion due to the WA and also different tolerances within the manufacturing process, if everything else is identical in relation.


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## neuroanatomist (Sep 2, 2016)

awinphoto said:


> neuroanatomist said:
> 
> 
> > awinphoto said:
> ...



A bit of a confusing explanation, IMO, and some misapplied concepts. The MFD has nothing to do with DoF per se (other than that combined with focal length determine the maximum magnification for a lens). 

Upshot: you can say DoF is determined by three factors – aperture, magnification, and sensor size (circle of confusion), or you can say it's determined by four factors – aperture, subject distance, focal length, and sensor size. 


Also:



awinphoto said:


> So that being said, a 5d will have shallower DOF in relations to a crop sensor because the crop sensor has a smaller capture area.



Sort of. The FF will have shallower DoF if you equalize the framing (move further away or use a wider lens), because that changes magnification. If you shoot with the same lens at the same distance, the DoF of the FF sensor will actually be (slightly) _deeper_. 




awinphoto said:


> Now cameras, depending on the MP and the lenses used, have a sweet spot as far as optimum focus... The more MP you have, the shallower DOF to get that sweet spot... such as around F5.6 for the 50D... Of course, on macro, that would still be very shallow, but it's a tradeoff. So the question would be are you looking for the most DOF, or sharp sharp images.... the sharpest images likely wont have the most DOF but that's something you will have to determine.



Might be good to introduce the term "diffraction" into this explanation, since that appears to be what you're talking about. More megapixels in the same size sensor means smaller pixels, and with smaller pixels the effects (softening) of diffraction become evident at wider apertures. Thus, as you stop down the lens for deeper depth of field, the higher MP sensor will be softer at the same narrow aperture.


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## awinphoto (Sep 2, 2016)

neuroanatomist said:


> awinphoto said:
> 
> 
> > neuroanatomist said:
> ...



Then again, yes and no.... perhaps instead of MFA it goes back to my original phrasing, distance of the lens to the subject. The point i was getting at with MFA is that will restrict the possibility to compare the lenses you brought into question. Perhaps that phrasing can be better coined as magnification, however, using a more fair comparison, take the 24-105, or the 24-70... go to that lenses min focus distance, at both extremes, everything else the same, take 2 photos, and then crop the WA to the portion seen by the telephoto side, and show them side by side at equal sizing, and the DOF will practically be identical... the telephoto will make it easier to see/appreciate the DOF up close and personal, i will give you that, BUT, in relation, the principles have not changed since the film era, in which i came from. 

I will agree if he's talking about diffraction, that's a whole new can of worms, however he will most likely with any modern camera sacrifice DOF for optimum focus


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## chauncey (Sep 2, 2016)

I'm not sure where we got into DOF as it is irrelevant to my question...lets say that you take a picture of a ruler, 
dead perpendicular to the lens with perfect focus...will a FF sensor with fewer MP out resolve a FF sensor with 30-50 MP?


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## Ph0t0 (Sep 3, 2016)

chauncey said:


> I'm not sure where we got into DOF as it is irrelevant to my question...lets say that you take a picture of a ruler,
> dead perpendicular to the lens with perfect focus...will a FF sensor with fewer MP out resolve a FF sensor with 30-50 MP?



Of course it will. The lower the MP count, the bigger the resolution. 
Why would you think otherwise?


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## scyrene (Sep 3, 2016)

chauncey said:


> I'm not sure where we got into DOF as it is irrelevant to my question...lets say that you take a picture of a ruler,
> dead perpendicular to the lens with perfect focus...will a FF sensor with fewer MP out resolve a FF sensor with 30-50 MP?



The higher the MP, *all other things being equal*, the more detail you resolve. Your question is a bit odd - what does 'fewer MP' mean? One tenth of a megapixel? One MP? Ten MP?

Think this way - the lowest resolution sensor is one pixel. Clearly, that cannot outresolve a four pixel sensor, or a ten pixel sensor, or a million pixel sensor. When you go higher than a certain point, you'll see increasing effects of diffraction at a given aperture on a per pixel level, and in real world shooting, camera shake will become more apparent, too. And lenses can only resolve so much detail. But you cannot lose resolution by increasing the number of MP. Your gains diminish the higher you go, but you will not lose resolution.


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## 3kramd5 (Sep 3, 2016)

Ph0t0 said:


> chauncey said:
> 
> 
> > I'm not sure where we got into DOF as it is irrelevant to my question...lets say that you take a picture of a ruler,
> ...



PhOtO wins the internet today.


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## Ph0t0 (Sep 3, 2016)

scyrene said:


> chauncey said:
> 
> 
> > I'm not sure where we got into DOF as it is irrelevant to my question...lets say that you take a picture of a ruler,
> ...



Chauncey, don't listen to Scyrene. Clearly Scyrene is just trying to confuse you with all the fancy talk. 
The main thing to remember is: The lower the MP count, the higher the resolving power.
And even if what Scyrene is saying would be true, you would still have the better option of using a lower MP body for shooting multiple images of fast moving subjects and later stitching those shoots into a single image with superior image quality.

You can learn more about that here--> http://www.canonrumors.com/forum/index.php?topic=30391.0


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## neuroanatomist (Sep 3, 2016)

awinphoto said:


> neuroanatomist said:
> 
> 
> > awinphoto said:
> ...



Nope, nothing equivocal about it. Remember the three blind men, one feels a rope, another a pillar, the third a snake? Magnification is the elephant. 

You discuss shooting with a tele lens compared to shooting wide and cropping. Shooting wide from the same distance means less magnification. Because one of the assumptions in calculating DoF is a fixed output size (e.g. 8x10"), cropping and enlarging to that fixed output size means more magnification. If you crop and enlarge so the subjects are the same final size, you've marched magnification – thus, given same sensor size and aperture, DoF will be the same. 

Like I said – aperture, magnification, and CoC.


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## neuroanatomist (Sep 3, 2016)

Ph0t0 said:


> Chauncey, don't listen to Scyrene. Clearly Scyrene is just trying to confuse you with all the fancy talk.
> The main thing to remember is: The lower the MP count, the higher the resolving power.



Yes, but the lower the MP count, the truer the dynamic sharperefic correction factor, which reduces resolving power if it gets too true.


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## jd7 (Sep 3, 2016)

neuroanatomist said:


> awinphoto said:
> 
> 
> > There are only really 3 things that control DOF of the image. The physical size of the sensor/film, the aperture settings, and the distance of the lens to the subject.
> ...



I have to say I thought DoF was controlled by sensor size, aperture and distance to subject, ie I thought what awinphoto said was technically correct.

To elaborate, my understanding is:

The reason you would get different depth of field with an 11-24/4 compared with a 600/4 (assuming the same f-stop, same sensor size and same distance to subject) is because, while the relative apertures would be the same in each case, the apertures would be very different (up to 6 mm for the 11-24, but up to 150 mm for the 600).

A lens remains the same regardless of the sensor size of the camera it is attached to, of course, but the performance of the camera/lens system is substantially influenced by sensor size. 

In particular, say you take a shot at 50 mm and f/2 with a full frame (35mm) camera. To get the same framing with the same lens and an APS-C camera (which is effectively cropping the image because of its smaller sensor size), you have to increase the distance to subject. So, a change in sensor size has prompted a change in distance to subject. Increased distance to subject increases DoF. So to counter that and get back to the same DoF as the original shot with the full frame camera, you would have to increase the aperture used for the APS-C shot.

If you take a shot at 50 mm and f/2 on the full frame camera, and then take a shot of the same scene from the same place with a 30 mm and f/2 on an APS-C camera, the images should be essentially the same in terms of framing (assuming same distance to subject). However, while the relative apertures were the same (f/2), the aperture used for the full frame shot is larger (25 mm compared with 15 mm), so again the full frame shot has shallower DoF. You would need to user a wider aperture for the APS-C shot to compensate.

As for magnification, it's related to focal length and distance to subject, but I did not think either magnification or focal length directly controlled DoF.

Am I missing something? This is certainly not the first time I've heard someone say magnification is a determinant of DoF, so perhaps I misunderstand how DoF works and I've got it all wrong?!?

Edit:
One factor I didn't mention above is that DoF is measured at a standard output size, so the image from a smaller sensor has to be enlarged more than the image from a larger sensor (assuming both sensors are smaller than the output size). The extra enlargement reduces DoF, suggesting a smaller sensor should have shallower DoF. However, as I understand it, the reduction in DoF due to extra enlargement is minor, and the other factors discussed above are much more important.


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## neuroanatomist (Sep 3, 2016)

jd7 said:


> I have to say I thought DoF was controlled by sensor size, aperture and distance to subject, ie I thought what awinphoto said was technically correct.
> 
> To elaborate, my understanding is:
> 
> ...



By using the physical aperture (iris diaphragm) diameter, you're combining (using that term loosely) focal length with aperture instead of distance. That's not wrong, but it's not the best approach because it's not universally applicable, nor is it the most convenient. I prefer easy methods that work 7 days a week, not complex methods or ones that only work on Tue-Sat. 

To give the simplest case where it breaks down, consider cropping an image, which changes the DoF. It's post-capture, so you're not changing the aperture (however you define it), nor are you changing the subject distance. However, you _are_ changing magnification. Now, technically you can state that cropping changes the circle of confusion, because in effect you're using a smaller sensor – and that would be another correct method. But for convenience, we treat CoC as a constant for a given sensor. 

Ultimately, all of these reduce to mathematical formulae, so they can be rearranged and have terms combined or separated algebraically. But I prefer magnification + aperture (+ CoC) as the simplest, most generally applicable method from a conceptual standpoint. Practically, focal length + distance + f-number (+ CoC) is probably most useful, because those three factors are what the photographer can directly control. 

Incidentally, awinphoto stated 'aperture _setting_' (f-number), distance, and sensor/film size, and that is certainly technically incorrect.


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## chauncey (Sep 3, 2016)

So, I can assume that the higher MP sensors do not translate into higher visual acuity, right?


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## Sporgon (Sep 3, 2016)

Maybe this is why I love my 5D (mark 1) so much


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## neuroanatomist (Sep 3, 2016)

chauncey said:


> So, I can assume that the higher MP sensors do not translate into higher visual acuity, right?



You can assume anything you like! Instead, I'd recommend downloading test scene RAW files from IR or DPR and comparing them yourself.


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## scyrene (Sep 3, 2016)

This thread has certainly increased my circle of confusion


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## chauncey (Sep 3, 2016)

> I'd recommend downloading test scene RAW files from IR or DPR and comparing them yourself.


I just did that and found nothing that would surpass my Ds3...especially using my stacking technique...until you exceeded ISO 400


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## neuroanatomist (Sep 3, 2016)

chauncey said:


> > I'd recommend downloading test scene RAW files from IR or DPR and comparing them yourself.
> 
> 
> I just did that and found nothing that would surpass my Ds3...especially using my stacking technique...until you exceeded ISO 400



Well, then...you have your answer.


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## jd7 (Sep 4, 2016)

neuroanatomist said:


> By using the physical aperture (iris diaphragm) diameter, you're combining (using that term loosely) focal length with aperture instead of distance. That's not wrong, but it's not the best approach because it's not universally applicable, nor is it the most convenient. I prefer easy methods that work 7 days a week, not complex methods or ones that only work on Tue-Sat.
> 
> To give the simplest case where it breaks down, consider cropping an image, which changes the DoF. It's post-capture, so you're not changing the aperture (however you define it), nor are you changing the subject distance. However, you _are_ changing magnification. Now, technically you can state that cropping changes the circle of confusion, because in effect you're using a smaller sensor – and that would be another correct method. But for convenience, we treat CoC as a constant for a given sensor.
> 
> Ultimately, all of these reduce to mathematical formulae, so they can be rearranged and have terms combined or separated algebraically. But I prefer magnification + aperture (+ CoC) as the simplest, most generally applicable method from a conceptual standpoint. Practically, focal length + distance + f-number (+ CoC) is probably most useful, because those three factors are what the photographer can directly control.



Thanks Neuro, I think I get all of that. The catch for me is that for whatever reason I don't find the magnification concept intuitive ... although I certainly take your point about its relevance, especially to cropping. Think I probably need to give all of this some more thought yet.



neuroanatomist said:


> Incidentally, awinphoto stated 'aperture _setting_' (f-number), distance, and sensor/film size, and that is certainly technically incorrect.


Ah, I'd missed that.


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## privatebydesign (Sep 4, 2016)

jd7 said:


> The catch for me is that for whatever reason I don't find the magnification concept intuitive ... although I certainly take your point about its relevance, especially to cropping. Think I probably need to give all of this some more thought yet.



This thread might help

http://www.canonrumors.com/forum/index.php?topic=15884.msg292745#msg292745


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## rrcphoto (Sep 4, 2016)

chauncey said:


> I do a fair amount of macro work...if image size is of less importance than is acute image sharpness,
> would I see a more acutely sharp IQ @ 300% by using a lower MP sensor (older) as opposed to one
> of the newer 30-50 MP beasts?
> 
> Am heavy into PS CC.



lol 300%

so three times the resolving capacity of the sensor .. got it.

neither would make a difference .. but why on earth would you choose a lower MP sensor .. versus a higher MP sensor where you wouldn't NEED go to 300% because you'd have more pixels on target?

as an example: if you look at 300% at a 12MP sensor - you only need to look at 150% on a 50MP sensor for the same relative magnification.


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## chauncey (Sep 4, 2016)

I routinely look at an image at that magnification to verify that my focus was good enough to cough out a print 
capable of having a nose-length viewing distance...it's an anal thingy.


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## privatebydesign (Sep 5, 2016)

chauncey said:


> I routinely look at an image at that magnification to verify that my focus was good enough to cough out a print
> capable of having a nose-length viewing distance...it's an anal thingy.



That makes no sense.

If you view at 300% then print at 360dpi you are judging focus at approx 10x print size, vastly higher than anybodies visual acuity.

That isn't anal, it is self destructive.


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## rs (Sep 5, 2016)

chauncey said:


> I routinely look at an image at that magnification to verify that my focus was good enough to cough out a print
> capable of having a nose-length viewing distance...it's an anal thingy.



You'd get better per pixel sharpness if you use a 5DsR, and downsample to 5.5 MP. There'd be no bayer interpolation, and even better, viewing it at 300% would return the same scale should you have left the original image alone and viewed it at 100%. :


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## jd7 (Sep 5, 2016)

privatebydesign said:


> jd7 said:
> 
> 
> > The catch for me is that for whatever reason I don't find the magnification concept intuitive ... although I certainly take your point about its relevance, especially to cropping. Think I probably need to give all of this some more thought yet.
> ...



Thanks PBD. I've only had a chance to have a quick look at that thread, but will read it properly in the near future.

I do get the idea that post-shot magnification matters - and that mean the size of the image you start with matters, and that will depend on sensor size and any cropping. The thing I don't find intuitive is the idea of magnification when taking the shot. Magnification will depend on distance to subject and focal length, but I didn't think focal length itself effected DoF (much). As I understand it, that leaves distance to subject, sensor size/image dimensions (allowing for cropping), and physical aperture (rather than relative aperture) as the determinants of DoF.

As Neuro says, there is a mathematical function for DoF and you can combine some of the terms in different ways. If I understand Neuro's earlier post properly, his preferred approach is to consider magnification (being a function of distance to subject and focal length) and aperture and CoC (as determined by the sensor size) as the determinants of DoF. At least at this point, I don't find it intuitive to think in those terms. Anyway, it seems there is more than one approach to DoF, but I like the idea of finding the simplest and most robust approach, so I'll keep working on it!


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## neuroanatomist (Sep 5, 2016)

jd7 said:


> Magnification will depend on distance to subject and focal length, but I didn't think focal length itself effected DoF (much). As I understand it, that leaves distance to subject, sensor size/image dimensions (allowing for cropping), and physical aperture (rather than relative aperture) as the determinants of DoF.
> 
> As Neuro says, there is a mathematical function for DoF and you can combine some of the terms in different ways.



Determinants are distance, focal length, aperture (f-stop), and CoC. Focal length has a significant effect...unless you divide it by f-stop, which removes both terms, so the determinants become distance, physical aperture, and CoC. I don't think most people, when out taking photos, think in terms of the diameter of the iris diaphragm in their lens, but rather in terms of focal length and f-stop, which they can directly choose.


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## chauncey (Sep 5, 2016)

> You'd get better per pixel sharpness if you use a 5DsR, and downsample to 5.5 MP. There'd be no bayer interpolation, and even better, viewing it at 300% would return the same scale should you have left the original image alone and viewed it at 100%


Now that is an interesting technique that I had not considered...will ponder that some more.


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## analoggrotto (Sep 5, 2016)

All this talk about AA filters...

*Has anybody modified a 5D Mark III with a clear filter to eliminate the Anti Aliasing (AA) layer? Lifepixel offers this service. *

For some reason, I cannot start my own thread about this matter, I am very curious if anybody has a modified vs unmodified comparison. 

And I for one am rather happy about this new 5D model. The III was not a revolutionary step above the II because it didnt need to be, Canon knows what they are doing and people know what they are getting when the pay big money for Canon. It isn't specs, it never was. How bad were the complaints when the Mark III was released? I hope they were as bad as some of what I hear now. 

If it works, then the price is well justified. I bought a car with a plastic radiator, so I waited for the warranty to expire and then I installed a pure metal one. 

I'm getting really tired of looking at sample swatches on dpreview, and making heads from tails of all the different parameters affecting that sample alter.


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