# Speculations on the megapixel race or "Do I need a + 32 Megapixel sensor?"



## tjshot (Oct 17, 2011)

Recent announcements of 24 Mpxls APS-C and rumors of 36 Mpxls full frame sensors seem to have changed the scenario for digital camera enthusiasts, triggering opposite reactions: some of us are out of the skin to get the new babies (I'm among them) while others seem to question the effectiveness of such upgrades.
We had similar doubts in the past when upgrading to higher density sensors and I've read many articles on the internet stating that you don't really need more than about 20 Mpxls full frame sensor (due to lense diffraction/aberration, sensor sampling performance etc.)

I hardly agree.

At the level of development we have reached today a small increase of pixel pitch (effective sampling rate -> sharpness and resolution boost) in the sensor will induce a much higher (square growth law) megapixel count, thus requiring much larger in-camera buffer memory, faster data saving channels, more powerful computers etc.

At the same time noise control becomes increasingly difficult (square growth law) due to higher amplification of the signal needed to achieve the same ISO rating; on the other side smaller pitch sensors seem to produce a much more even and defined noise, partly counterbalancing the degradation in quality (think about the terrible "pepper" grain in Canon EOS 5D compared to the smoother Canon EOS 7D).

Many additional elements factor in, resulting in final image quality: A/D converter performance (12bit to 14bit seems to produce a very high boost in dynamic range, noise performance etc.), image processor, firmware etc.

We'll eventually get to a break-even point where the pros in increased sampling capability will match cons in noise and data rate, when it comes to final image quality and system usability.

I believe we have not reached this point yet.

My take on the matter is that for full frame bodies 32-36 Mpxls still makes sense in terms of performance improvement; 32 Mpxls is probably a better trade-off for the advanced user.

In the attached PDF file I propose an in-depth analysis, based on software simulations matching available empirical data, of the expected performance for a 36 Mpxls full frame sensor compared to actual 21 Mpxls and also a hypothetical 50 Mpxls one.
Sharpness and resolution values in lpm are proposed, as well as some evaluations on performance increase.

The scenarios I describe offer me the general guidelines for future system upgrades, with a very probable step up to a + 32 Mpxls and an eventual move to 50 Mpxls if and when they'll become accessible; I don't see a good point in moving over that point, unless a totally new, cheap technology is developed.


----------



## J. McCabe (Oct 17, 2011)

I don't.

I'd much rather have ultra-wide lenses, which is why I'm waiting for the Nikon D800 announcement, and whether the rumored Nikon rectilinear 10mm lens would become a reality.


----------



## tjshot (Oct 17, 2011)

Wide lenses generally make sense for use with high res. sensors: the wider DOF lets you use the lense at optimal F-stops (F4 to F8) while keeping a significant portion of the image in-focus.
Moreover the rear focus rolloff at typical shooting (sensor to target) distances is more gradual than normal lenses or teles. 
That's a crucial requirement when printing to A3 + format from 35 mm: required DOF is much lower than manufacturer standard, as is the effective F-stop range ( aperture range that really benefit from higher sensor density).


----------



## tjshot (Oct 19, 2011)

It seems that with EOS-1D X Canon has covered the "super fast, sub 20 Mpxls" niche, appealing mostly to pros shooting sports and wildlife; of course it's marketed with a price tag matching that segment.

Obviously the camera will mark a new top score in low light and/or fast action, due to the larger sensor pitch (square growth in light chasing ability), a recent A/D converter and image processor; however it will not outperform the 5D MKII in resolution, after proper sharpening is applied.

EOS-1D X is not the cheaper, low Mpxls full frame body that would appeal actual advanced APS-C users not needing to print extra-large; maybe the same sensor with a slower processor and mechanics could fit such a body.
Production costs would benefit from the sinergy.

I still expect the 5D MK II replacement to implement a high megapixel full frame sensor, to appeal landscape shooters and general advanced users.
Competitors seem to have gone in that direction with a 36 Mpxls sensor; I see 32 or 33 Mpxls as better trade-off when it comes to noise / dynamic range performance and Canon has a long tradition in favouring those factors over absolute resolution.
I see an high-res sensor as unavoidable for Canon to keep the market share.


----------



## Canon-F1 (Oct 19, 2011)

i see it this way.

canon must have a good reason to choose 18 MP for itÂ´s new camera.
if they could have produced the camera with the same specs but 30 MP im sure they would have done that. donÂ´t you think so?

so it seems that CMOS (that includes foveon like sensors) and CCD sensor technology is slowing down.

and itÂ´s not as easy as producing faster CPUÂ´s for a computer.
for faster CPUÂ´s you make the DIE bigger or shrink the lithography process to put more transistors on the DIE. you can also hardcode special functions to speed up calculations.
but even CPUÂ´s running against a wall, for years we are around 4 GHz.

a 35mm FF sensor must have a certain size, you canÂ´t make it bigger.
unlike CPUÂ´s shrinking is not the holy grail.... smaller photosites will not help you increasing DR or reducing noise.
there is not much you can do when you reach a certain point of optimization.
you canÂ´t influence the absolut number of photons that reach the sensor area (of course you can, for example with flash... but i think you get what i mean  ) and you can not increase the absolut sensor area. 

you can only decrease the size of additional circuits to make more room for the photosites (as canon has done for the new sensor. sony has done it with itÂ´s backlit sensor), so the photosites can catch a greater percentage of photons.

sure you can always try to reduce the SNR but that will be expensive at a certain level.

new materials could help or a new sensor technology.
but i think we should get used to smaller steps in sensor development.



> however it will not outperform the 5D MKII in resolution, after proper sharpening is applied.



i say that depends on the AA filter thatÂ´s build in. but i have not done the math.
how is optimal resolution of the new 18 MP sensor compared to real world resolution of the 5D MK2 (i know that is unfair  ).

it may not outperform the 5D MK2.. but it could be a imperceptible difference.


----------



## candyman (Oct 19, 2011)

I am trying to get a good overview about why or why not more megapixel versus the IQ
I came up reading something that Ken Rockwell wrote when explaining settings for the Canon 7D:
"Image Size

No one really needs 18MP. All it does is slow everything and clog your hard drive, unless you're printing 10 feet wide.

Try shooting your 7D at its M (8MP) or S (4.5MP) settings. If you look at your images at 100%, you'll see that the lower resolution shots are sharper pixel-by-pixel!

When I'm photographing family and friends, I shoot at SMALL JPG. Even SMALL is good enough for great 20x30" prints.

The smaller-sized images out of the 7D are spectacular. They are sharper and cleaner than images from cameras on which that is their native resolution. The 7D always starts with 18MP, so it looks pretty good when you set the 7D to record at only 8MP or 4.5MP.

Why? Because they use less, or no, Bayer interpolation. No digital camera really resolves its rated resolution; they cheat and interpolate up, so at 100% at its rated resolution, no digital camera image is as sharp as a true scan from film.

At the 4.5MP setting, you have 100% R, G and B pixels, exactly as if you were using a Sigma Foveon sensor. If Sigma was selling this, they'd sell the 4.5MP (S) setting as if it were 13.5MP (also a lie).

What this means is that the lower resolution settings actually pack away lot more detail than you think. The S (4.5MP) setting of the 7D is a lot sharper than any 4.5MP camera.

M looks almost as good as L for the same reason.

If you're testing lenses, sure, shoot at L, but for everything else, try the settings for yourself, You'll probably get what you need at the smaller settings. For instance, the 11MP setting of the 7D has way more detail than any of the 12MP (native) Nikon cameras.

The resolution advantage of the 7D is obvious, even at lower settings. Try them.

I use LARGE for my scenic shots that I might print ten feet wide some day, but my family photos at 4.5MP, which is more than enough."

I am not into photography for billboards etc. Just sports/portrait/landscape - maximum A4 size.

Is there a second or third or... opinion on what Ken wrote? 
Thanks


----------



## Canon-F1 (Oct 19, 2011)

well ken rockwell..... :
the guy changes his opinion faster then his underwear.

then there is "looking sharp" and the actual amount of recorded information.

aliasing often looks pretty sharp to the human eye. 







tell me what looks sharper. 



> no digital camera image is as sharp as a true scan from film.



he once wrote he gets ~48-60 MP of real information from drum scanned 35mm film.
i doubt that.


----------



## tjshot (Oct 19, 2011)

Canon-F1 said:


> i see it this way.
> 
> canon must have a good reason to choose 18 MP for itÂ´s new camera.
> if they could have produced the camera with the same specs but 30 MP im sure they would have done that. donÂ´t you think so?
> ...



I mostly agree.
For a fast action camera the processing power and data bandwidht limits are the main constraints; larger files require longer times for processing and saving, while in-camera buffers are limited in size.
You also need a large photosite area to allow for a decent SNR ratio and support the framerate.
So the specs of a pro camera aimed to sports and wildlife shooters are more or less capped under 20 Mpxls; Nikon will probably follow the same route for the D4s or whatever they'll call the new pro sports camera.
Up to this day Canon has showed incredible skill in optimizing their sensors for catching the maximum amount of light for a given photosite size; they are working very close to theorical limits of actual electronics.
The incredible performance of EOS 7D, given its sampling rate, is a proof of this ability.
Resolution wise however I don't see a real boost in dropping the antialias filter: of course it would boost sharpness (sensor would behave closer to an order 2 MTF rolloff than actual order 3) but top resolution after proper sharpening would be more or less the same, i.E. very close to the same Nyquist limit.
Moreover I'm scared about high MTF values close to Nyquist limit of a sensor: artifacts become very frequent, specially for Bayer matrix sensors.
It's a bit better with Foveon, as there is no color Moire, but artifacts are present anyway (I've seen it happen frequently with my Sigma DP2x, a camera with a very fine normal lense).
I could break it down with a few simulation scenarios when I get the time.
Safer zone to start dropping antialias filters for Bayer sensors is around 4 micron photosite pitch, i.e. close to 50 Mpxls; MTF should not be much higher than 10% there, even for an excellent full frame lense.
I believe Canon actually owns the CMOS technology to produce a 32 Mpxls full frame sensor with noise/dynamic range performance equal or superior to EOS 5D MK II, providing a good resolution boost with no practical drawback. 
It would be targeting a different, probably more profitable, market share than 1D-X


----------



## Canon-F1 (Oct 19, 2011)

tjshot said:


> I believe they actually own the CMOS technology to produce a 32 Mpxls full frame sensor with noise/dynamic range performance equal or superior to EOS 5D MK II, providing a good resolution boost with no practical drawback.



i think so.
but it would cost.. less DR and i think more noise then the 1D X when they use the same sensor technology. 

but what does 32 MP compared to 21 MP means for resolution?
to double the resolution you would need a 84 MP camera (compared to the 5D MK2).
less if you remove the AA filter.

still itÂ´s small steps.


----------



## tjshot (Oct 19, 2011)

Canon-F1 said:


> tjshot said:
> 
> 
> > I believe they actually own the CMOS technology to produce a 32 Mpxls full frame sensor with noise/dynamic range performance equal or superior to EOS 5D MK II, providing a good resolution boost with no practical drawback.
> ...



It's more or less 10 lpm at every stop in MTF 50% values, more for MTF 10%.
Good to have for the same price if there are no other drawbacks.


----------



## torger (Oct 19, 2011)

Canon-F1 said:


> but what does 32 MP compared to 21 MP means for resolution?
> to double the resolution you would need a 84 MP camera (compared to the 5D MK2).
> less if you remove the AA filter.
> 
> still itÂ´s small steps.



21 MP = 5610 x 3740
32 MP = 6930 x 4620

roughly 23% increase in x and y resolution. When over 30 megapixels I think it should be combined with dropping the AA filter, the higher the resolution the less likely moire will be a problem.

A 23% increase is not huge, but enough for me to think it is attractive. It is also about getting resolution high enough for the formats I like to print (fine art landscape prints). I like 50-60 cm (20-25 inch) on the short side and keeping resolution at 200 ppi or higher, and then 32 megapixels is still a bit low, but the more I get the closer I get to the goal. For smaller prints I like higher print density 300-400 ppi depending on print technology so the resolution requirement does not really change.


----------



## Kobayashi (Oct 19, 2011)

I found it funny that until now, everyone was moaning and b^tching that Canon is stupid, what`s with all that megapixels, you don`t need too many to create art, and all that. I remember clearly when the 7D and 5D2 went out, and almost everyone complained about the increase in megapixels, some switched to Nikon because of it, fists were thrown in the air, diffraction charts appeared, and all that circus.
Now, Canon listens to most of what people were saying back then, releasing this speed/low light monster, and of course, it`s no good. Not enough megapixels! ;D And for those who are trying to say that storage isn`t an issue, well, the issue isn`t about storage at all. Of course it`s cheap, but processing power ain`t. And with 12fps under the belt, it`s easy to get carried away and then get annoyed trying to sort through all that. 

Now on topic, personally i think 18 mp is enough for the time being. I`m also stuck with low mp dslr (10mp), but nobody when seeing my pictures could tell that, and since i try to be careful composing my shot, i rarely need to crop.
I`m really interesting to see what this new sensor can muster in terms of low light abilities, and i`m drooling over it, i think it`s more important to get the shot and be able to USE those extra stops of light, than end up with 36 megapixels of soft, noisy and unusable.


----------



## torger (Oct 19, 2011)

Kobayashi said:


> I found it funny...



On the forums, it is more likely to see criticism than praise. So when it comes a high megapixel slow camera the fine art photographers are silent and the action shooters complain, and now it is the other way around .

Photography is incredibly diverse there are so many genres all with the different needs. For example sports photography and landscape photography is totally different. Depending on where your interest is you demand different things from a camera. Technology has not evolved so far that it is possible to make a one-size-fits-all camera.


----------



## tjshot (Oct 19, 2011)

Kobayashi said:


> I found it funny that until now, everyone was moaning and b^tching that Canon is stupid, what`s with all that megapixels, you don`t need too many to create art, and all that. I remember clearly when the 7D and 5D2 went out, and almost everyone complained about the increase in megapixels, some switched to Nikon because of it, fists were thrown in the air, diffraction charts appeared, and all that circus.
> Now, Canon listens to most of what people were saying back then, releasing this speed/low light monster, and of course, it`s no good. Not enough megapixels! ;D And for those who are trying to say that storage isn`t an issue, well, the issue isn`t about storage at all. Of course it`s cheap, but processing power ain`t. And with 12fps under the belt, it`s easy to get carried away and then get annoyed trying to sort through all that.
> 
> Now on topic, personally i think 18 mp is enough for the time being. I`m also stuck with low mp dslr (10mp), but nobody when seeing my pictures could tell that, and since i try to be careful composing my shot, i rarely need to crop.
> I`m really interesting to see what this new sensor can muster in terms of low light abilities, and i`m drooling over it, i think it`s more important to get the shot and be able to USE those extra stops of light, than end up with 36 megapixels of soft, noisy and unusable.



Nobody is really complaining about low megapixels: 18 Mpxls on the D1-X just fit the intended use of the camera.
For landscape however I see an higher res sensor as a better fit.
But we are talking about very different use scenarios.


----------



## macfly (Oct 19, 2011)

TJ, great article, thank you, it was nice to get all that info clearly laid out.

In your final but on paragraph you mention the limits of the APS, but I confess that the NEX-7 has caught my eye as a replacement to yhe G12 , a camera that was a big step backwards. Reading the blogs it seems that the lenses are the let down for the NEX cameras at the moment, but maybe Zeiss or similar will react to what I suspect with be their popularity, and make some great glass.

I cancelled my order for the new Canon on reviewing the specs, because it simply doesn't provide what I need and want, a camera to get close to bettering the H2 system (with Phase P65) at 100iso. I realize on this board I'm in a huge minority who only care about peak performance at 100iso, but it is pretty much the only iso I'll shot at, and if the lights low I use a tripod.

I'm hoping the new Sony/Nikon 36mp sensor will provide what I want, fingers crossed.


----------



## drmikeinpdx (Oct 19, 2011)

"think about the terrible "pepper" grain in Canon EOS 5D compared to the smoother Canon EOS 7D."

What a coincidence! I have a 5D and a 7D. I think the 7D has what you might call "pepper grain" compared to the smoother tonal details of the 5D. I hate using the 7D for portraits, but it sure is nice for action.

I am working on ways to get better images with the 7D by making changes in post-processing. I am finding that if you shoot RAW, it makes a huge difference how you do your post processing. If you shoot JPGs, your in-camera settings make a huge difference.

I think the lesson here is that it is very difficult to compare the image quality of two different cameras. No matter which one you have, you will learn to process your images to get what you want.

Mike
Portland, OR


----------



## tjshot (Oct 20, 2011)

macfly said:


> TJ, great article, thank you, it was nice to get all that info clearly laid out.
> 
> In your final but on paragraph you mention the limits of the APS, but I confess that the NEX-7 has caught my eye as a replacement to yhe G12 , a camera that was a big step backwards. Reading the blogs it seems that the lenses are the let down for the NEX cameras at the moment, but maybe Zeiss or similar will react to what I suspect with be their popularity, and make some great glass.
> 
> ...



For compact cameras, as for DSLRs, my choice has always been driven by max expected print size: I try to avoid interpolation as much as I can.
For me 5x7 inches print is the standard for casual shots from compact cameras, that's why I settled for a Sigma DP2x, as it sports the best sharpness and noise for that size.
NEX series cameras have great sensors and compact bodies, but they are aimed for larger prints; lenses however are pretty bulky and often compromise the portability of the system.
This is true also for other mirrorless compact systems.
What they lack is a relly good series of pancake primes in different focal lenghts.

About your specific requirements in low iso shooting, I don't think a CMOS full frame DSLR will ever get close to your actual medium format system.
The Phase One P65 is a very good digital back and a good match for quality medium format lenses.
Quality medium format lenses generally have a peak performance at F 11; moreover DoF requirements will force you to shoot 1 - 1.5 stops down compared to 35mm, assuming equivalent focal lengths.
Following previous assumptions, top MTF 50% value for a real shooting scenario is about 55 lpm.
Top MTF values for the P65 + real quality lense would be:
Unsharpened MTF 50% 40 MTF 10% 78
Sharpened MTF 50% 70 MTF 10% 82 with k= 0.55 (boost) and r=1 (radius)

Taking into account the size difference of diagonal for the two sensors, the ratio to 35mm full frame is 0.64, which translates into following equivalent MTF values:

Unsharpened MTF 50% 62 MTF 10% 122
Sharpened MTF 50% 109 MTF 10% 128 with k= 0.55 (boost) and r=1 (radius)

(Warning: The above equivalence should be worth only as a rough performance comparison, as the MTF values for different sensor sizes are not directly comparable: for example when you print (or enlarge) to the same size a same image taken with two different sensors, you are really relying on different MTF zones for the same limiting lpm value in the print. It could be MTF 30% from the smaller sensor and MTF 50% for the bigger one, which will appear cleaner (still far from the visible noise level) and sharper (more contrast for the same detail).
It's different from comparing values for the same MTF 50% or MTF 10% levels.)

Even a 50 Mpxls full frame sensor 35mm with the best real lense would not deliver similar values, falling short of 20 lpm in MTF 50% and 10-15 lpm in MTF 10%.
Resolution would be close, but difference in sharpness would be quite relevant.
However, SNR ratio, Dynamic range and tonal separation would still be much better with the P65 back.

So, given your typical shooting scenario, your actual digital back is your best option.


----------



## PeterJ (Oct 20, 2011)

tjshot said:


> Many additional elements factor in, resulting in final image quality: A/D converter performance (12bit to 14bit seems to produce a very high boost in dynamic range, noise performance etc.), image processor, firmware etc.


Excellent summary, on the above point for some reason I got smited last time I mentioned it up but a lot of people don't realise a high-speed ADC at 14 bit resolution is pretty cutting-edge when they want the extra DR we all desire. I just checked Analog Devices and their fastest 16-bit converter costs over $US100 for 250MSPS which you'd need for 32MP x 8fps but according to their datasheet only has a little over 12 bits of effective resolution.

What you can do is us more accurate but slower ADCs in parallel which is what Canon have done with the new X model by using 16 in parallel I believe to get a fast reading time. For comparison I'm doing a job at the moment with a delta-sigma ADC that has 22 bits effective resolution, it costs < $5 but runs at around 10 samples per second, so capturing 32MP at that rate would take over a month.


----------



## tjshot (Oct 20, 2011)

PeterJ said:


> tjshot said:
> 
> 
> > Many additional elements factor in, resulting in final image quality: A/D converter performance (12bit to 14bit seems to produce a very high boost in dynamic range, noise performance etc.), image processor, firmware etc.
> ...



I absolutely agree. 
Hope Canon has followed the same "parallel processing" route shown with EOS 1D-X for the next high res body.
Frame rate would not be crucial for intended use, so maybe reducing parallel A/D units could help cutting down the costs.
I believe A/D converter performance to be crucial for coping with Dynamic Range and Noise from smaller pitch sensors; in fact it seems to be the main component involved in squeezing a clean image and better performance out of the same sensor area.
The new Phase One IQ 180 digital back uses 16bit A/D units and it seems to pay off, at least for low ISO; I wander if the amount of light reaching a "sub 5 micron" photosite is really enough to benefit from the extended bit depth. It was for 14bit.
Probably frame rate and processing speed constraints have driven the choice for EOS 1D-X but I believe the bit depth of encoders employed in the next high res bodies, be it Canon , Nikon or Sony, will tell us if the upgrade is profitable/effective.


----------



## motorhead (Oct 20, 2011)

To try and stop progress is a waste of time and to me the ever increasing mp count is always going to be heading upwards. I am happy that this is the case, I believe the benefits of 200 to 1000mp files when we reach those heady numbers will be far smoother colour graduation and tonal qualities, not just the normal issues that others constantly mention.

I was very depressed when the 1Dx was first mentioned here, but thinking more about what Canon have said in the past about the 1Ds being radically changed gives me hope. Just because the current 1Ds mk3 has been discontinued does not mean that Canon will ignore those professionals who need the high mp counts. I believe its just that the rapidly approaching 2012 Olympics mean that the 1D update was more urgent.


----------



## Chewy734 (Oct 20, 2011)

tjshot, thanks for the writeup... I appreciate the time you took to write that article.


----------



## tjshot (Oct 20, 2011)

Chewy734 said:


> tjshot, thanks for the writeup... I appreciate the time you took to write that article.



Not at all!
It really was written out of personal curiosity.


----------



## GeorgeMaciver (Oct 20, 2011)

Thanks for that article by Ken Rockwell, Candyman, I'm planning lowering the resolution of my RAWs next time I'm out, to test out what he says.

8)


----------



## torger (Oct 20, 2011)

On the print side, doesn't anyone do c-prints any longer? I find it quite nice to order large prints from the lab. I usually do a couple of smaller test prints to verify color, brightness etc and then order the final size for fine art framing. Unlike ordering inkjet prints, c-print results are very predictable, those machines are kind of fool-proof. The main drawback is that you really only can get a single glossy photo look, there is not the wide choice of papers as for inkjets. But if you like glossy c-print is one of the best.

What I'm saying is that you don't need to be a pro to do prints larger than 13x19. To me it is more common that I do prints which is larger than this format than the other way around.

Another thing is that in 30 years I may want to make prints of pictures I made this year. I don't know what print technology will exist then. So I don't really like to limit the camera sensor to commonly available print technology if you don't need to.


----------



## tjshot (Oct 21, 2011)

torger said:


> What I'm saying is that you don't need to be a pro to do prints larger than 13x19. To me it is more common that I do prints which is larger than this format than the other way around.
> 
> Another thing is that in 30 years I may want to make prints of pictures I made this year. I don't know what print technology will exist then. So I don't really like to limit the camera sensor to commonly available print technology if you don't need to.



For me it's more a matter of optimizing investment to actual requirements: I'd rather put my money on an pro lens that will stay with me for years, than on a (relatively) short-lived camera body.
So I just choose the camera accordingly.
Moreover I see 13x19 inches from a single shot as the perfect top size for quality personal prints: archive size is still manageable and they are big enough to appreciate fine details.
If I'll ever need to print the same image larger I could still interpolate with decent results or do digital mosaics; with a bit of knowledge even a cheap pano setup can give excellent results.
Thats why I look forward to a 32 Mpxls body, as it perfectly fits my needs.
Every further increase in res. should be evaluated against noise and dynamic range performance.


----------



## torger (Oct 21, 2011)

tjshot said:


> Thats why I look forward to a 32 Mpxls body, as it perfectly fits my needs.
> Every further increase in res. should be evaluated against noise and dynamic range performance.



I shall say that also agree that 32 megapixels would be an excellent resolution for 5Dmk3, especially without AA filter. Above 30 it will be much about lens resolving power anyway. High contrast pixels at 32 megapixels (thanks to a sharp lens and no AA filter) could give a sharper image in print than low contrast at 45...

Already today the APS-C cameras 18 megapixels is kind of out-resolving lenses, the individual pixels are not particularly high contrast. You may be getting almost the same resolution from a 12 megapixel fullframe camera as from an 18 megapixel APS-C, depending on lens.

I don't see it as a big disadvantage to out-resolve lenses though, with bayer array it can be nice to out-resolve a little, and if you need to rotate or perspective adjust the image it can be nice to have "soft" pixels since you will not reduce image quality as much as if the pixels are supersharp. Deconvolution can also restore a bit of the resolution. However, if there is DR and noise gains to have larger pixels that will be more valuable before starting to outresolve lenses.

32 seems like a good number today, because then you both increase the resolution significantly but still have larger pixels than on the modern APS-C sensors.


----------



## tjshot (Oct 24, 2011)

torger said:


> tjshot said:
> 
> 
> > Thats why I look forward to a 32 Mpxls body, as it perfectly fits my needs.
> ...



The concept of a sensor "outresolving" a lense is prone to many _caveat_s.
Borrowing some infos from the document attached to original post, one could assume that to capture information from a real, excellent lense up to the MTF 10% (relevant resolution) a sensor would need to resolve:

about 90 lpm at F 16
about 135 lpm at F 11
about 159 lpm at F 8
about 195 lpm at F 5.6

Even a 50 Mpxls full frame sensor, or an equivalent-pitch 18 Mpxls APS-C one (EOS 7D), with proper sharpening applied, would be limited to about 115 lpm at MTF 10%: it would fall short of 20 lpm to reach the 135 lpm provided by the lense at F11.
For F 8 and F 5.6 the limit is even higher and would require an extremely dense sensor pitch, unpractical for actual CMOS technology due to poor noise and dynamic range performance.
Even a lense of average quality, in the F 4 to F 11 range, would probably be delivering "more information" than a 50 Mpxls sensor can actually resolve.

But the main thing to keep in mind is that limiting resolution, or Nyquist limit for a digital sensor, is not the only element to consider when evaluating performance.
A denser pixel pitch, after proper sharpening, can squeeze more information out of the same lense than a larger pitch one, even when the lense is performing below the Nyquist limit of both sensors (for example stopped down to F16 or smaller).
In other words the same lense stopped down to F16 would deliver better sharpness and resolution on a 50 Mpxls sensor than on a 36 or 21 Mpxls one, after proper sharpening is applied.
This is mainly due to the fact that a denser pitch generally allows to push sharpening further, for a similar SNR (Signal to Noise) ratio; moreover the higher Nyquist limit will allow to recover and sharpen even the high frequency information that a lower Nyquist limit would cut off. 
Thus on a 50 Mpxls sensor you can squeeze 115 lpm @ MTF 10% out of an excellent lense stopped down to F16.
The main constraint is keeping up the SNR for smaller photosites so that they can produce a clean image and consequent better sharpening; up to this day it's been possible, mainly upgrading A/D converters to higher bit depth units, using better microlenses and optimizing the electronics.

So the whole imaging chain, i.e. lense + sensor, should be considered when evaluating performance: considering the lense only, then assuming a sensor would be "outresolving" it due to its higher Nyquist limit, is simply uncorrect.

For actual CMOS technology I believe a 32 Mpxls full frame sensor to be the optimal compromise and 50 Mpxls full frame sensor to be the practical limit ( if ever fast and effective 16 bit A/D converters can be introduced).


----------



## torger (Oct 24, 2011)

tjshot said:


> The concept of a sensor "outresolving" a lense is prone to many _caveat_s.
> Borrowing some infos from the document attached to original post, one could assume that to capture information from a real, excellent lense up to the MTF 10% (relevant resolution) a sensor would need to resolve:



Yes "outresolving" is a simplified way to see it. Lens resolution is not a gating limit, even if you improve a factor in the chain that is not the largest "blur factor" the resolution will improve. However, you start to see diminishing returns when increasing sensor resolution over some limit, and how far you think it is meaningful to go is a matter of taste. With 18 megapixels on APS-C I think the point of diminishing returns has been passed, so I don't see it meaningful to increase it further.

My guess is that it is not meaningful to have such high resolution on the sensor that you can resolve down to MTF10% of the best part (center) of the best lenses. If combined with some clever deconvolution sharpening it perhaps can be, but unprocessed no.

It would be interesting to make a practical test with state of the art sharpening techniques and prints etc to find out how high resolution you need from a sensor relative your lens. I think the result would be that you need considerably less sensor resolution than the theoretical max.


----------



## Edwin Herdman (Oct 25, 2011)

I'm trying to work through the attached PDF article, but the sans serif Courier New font makes it unreadable. Next time please use a serif font, for the love of my eyes.


----------



## tjshot (Oct 25, 2011)

Edwin Herdman said:


> I'm trying to work through the attached PDF article, but the sans serif Courier New font makes it unreadable. Next time please use a serif font, for the love of my eyes.



Sorry! 
I'll keep it in mind for the follow up I'll be posting in a few days, about sensor performance for a given print dpi and size.


----------



## AprilForever (Oct 25, 2011)

I like megapixels. The more the merrier! But, I have reasons for liking them... Usually, my subject of choice, birds in flight, don't fill the frame, and often don't even come close to filling it...

The more the merrier! And hand me that stack of hard drives...


----------



## tjshot (Nov 1, 2011)

AprilForever said:


> Usually, my subject of choice, birds in flight, don't fill the frame, and often don't even come close to filling it...



That's the only situation in which a smaller sensor may perform better than a full frame one.
The same focal lenght will produce a "closer crop" with an higher pixel pitch.
Depending on the crop factor and pixel pitch density it can translate in better resolution and sharpness in final image.
For a given print size, the same F-stop will deliver a smaller DoF on crop sensor than on full frame, with worse SNR and Tone Separation for same ISO setting; however the higher sampling capability can eventualy make up for this cons.

If you often find yourself short of reach even with your most powerful tele, than a denser, smaller sensor is definitely the best choice.


----------



## Edwin Herdman (Nov 4, 2011)

That is actually a more common scenario than just bird photography: Your best light prime lens can frame a speaker more tightly from the back of the room, or your fastest affordable f/1.4 lens (the 50mm) covers the very popular 80mm focal length range.

So it's not just reach - it's also price and weight, and possibly has other advantages as well (for example, try shooting a high resolution image on full frame with a 135mm tilt-shift lens - APS-C gets you much closer to this reality unless you're happy with the aperture and quality loss of coupling a 1.4X EF extender - and the 2X does nothing great for the TS-E 90mm).


----------



## tjshot (Nov 4, 2011)

Edwin Herdman said:


> So it's not just reach - it's also price and weight, and possibly has other advantages as well (for example, try shooting a high resolution image on full frame with a 135mm tilt-shift lens - APS-C gets you much closer to this reality unless you're happy with the aperture and quality loss of coupling a 1.4X EF extender - and the 2X does nothing great for the TS-E 90mm).



I agree. There are situations where reduced FoV from crop sensors comes in handy.
However excellent prime lenses are required to really exploit the denser sensor pitch.

When it comes to tilt/shift lenses, for me DoF is the real constraint: I mainly use tilt to extend DoF for landscape shots, while I don't really feel the need to use it to isolate focus as long focal lenses do a good job wide open.
Enlarging to the same print size (A3 or more), full frame barely delivers enough DoF for a sharp down-tilt landscape shot, and that is for 24mm focal lenght or shorter (17mm). Even a 50mm is unusable in this scenario.
APS-C sensors simply don't provide enought depth to cover a large print.
That's the main reason why I still stick to using some film large format: there is no option in digital if you need a lot of DoF from a longer (equivalent) focal lense.


----------



## Edwin Herdman (Nov 4, 2011)

Tilting the plane of deep focus is certainly more restricted on an APS-C camera than on a FF camera, but again this is a necessary evil for some applications because APS-C gives you (currently, and for the foreseeable future) the densest resolution for the longer framing. I mention TS-E lenses (and the same applies to macro lenses) not because the shift or tilt changes the rationale, but because there simply isn't any degree of tilt or shift available on lenses in focal length lenses longer than 90mm (unless you go to the very expensive Hartblei Superrotator 120 f/4 Makro lens).

While I haven't been able to do much for the near-macro capabilities of the TS-E 90mm on APS-C while also using tilt and shift (the effects of tilt especially are less pronounced close up, in seemingly the same way that the DOF slice is wider the further from the sensor plane you get), it's nice to have any control at all.

Also don't agree that you need a great prime to "really exploit" denser resolution sensors - new zooms are up to the standard, including top zoom lenses from Canon and Sigma. New primes might go even farther but for practical purposes the zooms are often more than enough - it's a sign how far things have come in a short time (only twelve years, from 1996-2008) that a 70-200mm f/2.8 IS II is actually sharper than the fixed 200mm f/2.8 non-IS.


----------



## tjshot (Nov 4, 2011)

Edwin Herdman said:


> Also don't agree that you need a great prime to "really exploit" denser resolution sensors - new zooms are up to the standard, including top zoom lenses from Canon and Sigma. New primes might go even farther but for practical purposes the zooms are often more than enough - it's a sign how far things have come in a short time (only twelve years, from 1996-2008) that a 70-200mm f/2.8 IS II is actually sharper than the fixed 200mm f/2.8 non-IS.


I was thinking more about lense performance wide open than pure resolving power: for an APS-C sensor compared to a full-frame one, having to cope with lower SNR ratio for the same ISO setting, a good lense performance at F 2.8 and above can make the difference.
Many recent primes behave outstandingly well in the center up to F 1.4, allowing for the use of optimal low-ISO settings.


----------



## AprilForever (Nov 7, 2011)

tjshot said:


> At the level of development we have reached today a small increase of pixel pitch (effective sampling rate -> sharpness and resolution boost) in the sensor will induce a much higher (square growth law) megapixel count, thus requiring much larger in-camera buffer memory, faster data saving channels, more powerful computers etc.
> 
> At the same time noise control becomes increasingly difficult (square growth law) due to higher amplification of the signal needed to achieve the same ISO rating; on the other side smaller pitch sensors seem to produce a much more even and defined noise, partly counterbalancing the degradation in quality (think about the terrible "pepper" grain in Canon EOS 5D compared to the smoother Canon EOS 7D).



Solution: We must use round pixels on a round sensor! The square problems will be a thing of the past!!! (actually I have seen something about hexagonal pixels...)

I love more megapixels. And we all should. As the technology progresses, things will get better and better!The 7D is hugely better than the 300D. The future cameras will gradually get better than the current ones. And more megapixels is a part of this growth.


----------

