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Author Topic: Speculations on the megapixel race or "Do I need a + 32 Megapixel sensor?"  (Read 13030 times)

tjshot

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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

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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

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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

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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

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i see it this way.

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

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

and it´s not as easy as producing faster CPU´s for a computer.
for faster CPU´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 CPU´s running against a wall, for years we are around 4 GHz.

a 35mm FF sensor must have a certain size, you can´t make it bigger.
unlike CPU´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 can´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 it´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.

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

i say that depends on the AA filter that´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.
« Last Edit: October 19, 2011, 05:50:45 AM by Canon-F1 »
6D, 5D MK2, 7D, 550D... a lot of Glass.

candyman

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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


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Canon-F1

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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. :)

Quote
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.
« Last Edit: October 19, 2011, 06:01:17 AM by Canon-F1 »
6D, 5D MK2, 7D, 550D... a lot of Glass.

tjshot

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i see it this way.

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

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

and it´s not as easy as producing faster CPU´s for a computer.
for faster CPU´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 CPU´s running against a wall, for years we are around 4 GHz.

a 35mm FF sensor must have a certain size, you can´t make it bigger.
unlike CPU´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 can´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 it´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.

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

i say that depends on the AA filter that´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.

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
« Last Edit: October 19, 2011, 06:21:58 AM by tjshot »

Canon-F1

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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 it´s small steps.
« Last Edit: October 19, 2011, 06:16:26 AM by Canon-F1 »
6D, 5D MK2, 7D, 550D... a lot of Glass.

tjshot

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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 more noise then the 1D X when they use the same senor technology.
 
but what does 32 MP compared to 21 MP means for resolution?
to double the resolution you would need a 84 MP camera.

it´s small steps.

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

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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 it´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

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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

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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

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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

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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.
« Last Edit: October 19, 2011, 11:13:19 AM by macfly »