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Thread: Big pixels or Little pixles?

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    Default Big pixels or Little pixles?

    With a lot of cameras coming out lately with wildly different sized pixels, there are more choices than ever, and seemingly more confusion than ever. Large pixels alone do not improve high ISO noise performance. With the same lens at the same imaging position, larger pixels have less pixels on the subject, thus each pixel sees a larger area, which gathers more light, but there is less detail in the image. If you had very small pixels, one could average pixels together and improve signal-to-noise per pixel by trading detail and noise. Less noise and less detail, or more detail with more noise. So which to choose, a camera with larger pixels or smaller pixels?

    In the subsequent posts to this thread, I'll show a series of images taken with 3 cameras, each with different sized pixels. The subject (the moon) was small in the frame, so this is a focal length limited situation. I used a 300 mm f/2.8 lens on the 3 cameras. The exposure = 1/ISO at f/5.6 on each camera. So each sensor received the same amount of light at a given ISO. The 3 cameras have 4.3, 5.7 and 6.4 micron pixels. The 6.4 micron pixel images have the highest signal-to-noise ratio, but the least detail. The images were converted from raw with identical settings on all images.

    Your job, if interested, is to examine the series and evaluate which camera produces the best image at each ISO for this condition. (Note: a frame filling subject will produce different results.)

    Roger
    Last edited by Roger Clark; 03-02-2012 at 12:02 AM.

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    The ISO 100 set.

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    The ISO 800 set.

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    The iso1600 set.

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    The iso3200 set.

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    The iso6400 set.

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    Very good points Roger,

    this is one of the topics where things get complicated as you factor in real-world situations, For your subject (focal-length limited, high contrast subject, no color detail) I'd pick the small pixel camera and do advanced image processing to recover the details/remove noise.

    For bird photography there are too many factors, especially when you have different sensor size and thus different FOV, it really depends on how much closer you can get, what is the purpose of final image, etc. For my style of photography, a larger sensor will often provide better IQ because I can get closer to the subject and collect more light at the same FOV. But that doesn't apply to everyone. So I don't think there is one answer...a larger sensor with too few pixels is not ideal either...

    I think a better way is to fix sensor size and just examine pixel size alone (like the 5D3 vs. D800) both receive the same number of photons but just divide them differently. In principal since Shot noise is white you can recover the SNR of the large pixel by averaging the smaller pixels as we all know. In practice however the Demosaic makes things complicated. How exactly the demosaic process affects the noise PSD around the Nyquist depends on the particular algorithm. For e.g. some RAW convertors like ACR result in color blotches or large grain that are a few pixels large. Some RAW converters produce very fine grain that is around Nyquist frequency. Of course the spectrum is no longer white in the former case and down-sampling in that case doesn't quite recover the SNR of the larger pixel because of the correlation induced by the demosaic algorithm ....There is also complications from read noise in the shadow areas...if read noise is patterned (FPN) down-sampling can actually make it worse because it makes the low frequency harmonics more dominant once the random component has been reducing by low-pass filtering. So overall especially for subjects like feathers that have low-contrast detail preserving this detail becomes difficult at high ISOs with very small pixels...

    On the other hand, with scaling of pixels, cross talk (optical and electrical), read noise, reset noise as well as QE improves so when comparing cameras of different generation the newer camera usually comes out better. Here is a ISO 3200 file from the Nikon D800, which has been processed (poorly because I did not have the RAW file) and down-sampled to 12 Mpixles (native D700/D3 size). I think everyone would agree that it looks better than the output from those cameras... http://www.arihazeghiphotography.com/photos/D800NR.jpg The D800 is a perfect example of Moore's law for image sensors!

    I think there is crossover ISO from which point it becomes practically impossible with commercial image processing software to recover the SNR of the large pixel 5D3 from a small pixel D800 output. My wild guess is that the crossover is probably just above ISO 6400 or higher (may 12K). Since most wildlife images are not made at night, I think Nikon's approach is best in this case for wildlife photographers. When light is that poor, avian photos usually suck so those insane high ISOs aren't really useful in bird photography IMHO.

    I think a few years ago we concluded the optimal pixel size was 5.6um but now it seems with technology scaling the optimal size is close to where D7000/D800 land which is 4.8um...of course for general applications, for specific applications where absolute low light performance is needed it is probably better to stick with large pixels for a clean file out of the camera with minimal post processing and small file size...

    Any ways good discussion, I am not sure what the future road map for Canon is now that they have announced major pro bodies for the next 3 years...
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    Quote Originally Posted by arash_hazeghi View Post
    I think a better way is to fix sensor size and just examine pixel size alone (like the 5D3 vs. D800) both receive the same number of photons but just divide them differently. In principal since Shot noise is white you can recover the SNR of the large pixel by averaging the smaller pixels as we all know. In practice however the Demosaic makes things complicated. How exactly the demosaic process affects the noise PSD around the Nyquist depends on the particular algorithm. For e.g. some RAW convertors like ACR result in color blotches or large grain that are a few pixels large. Some RAW converters produce very fine grain that is around Nyquist frequency. Of course the spectrum is no longer white in the former case and down-sampling in that case doesn't quite recover the SNR of the larger pixel because of the correlation induced by the demosaic algorithm ....There is also complications from read noise in the shadow areas...if read noise is patterned (FPN) down-sampling can actually make it worse because it makes the low frequency harmonics more dominant once the random component has been reducing by low-pass filtering. So overall especially for subjects like feathers that have low-contrast detail preserving this detail becomes difficult at high ISOs with very small pixels...
    Arash,

    Greetings. The above is just a great paragraph. Thanks much.

    Cheers,

    -Michael-

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    Roger- Whether is should theoretically or not, in all the images the 7D shows more noise than the 1DIV or 5DII, which seem more or less equivalent (5DII appears slightly better). For me this is a big factor that outweighs the extra detail in the 7D image and is one reason I love my 1DIV and 5DII so much! Less noise for me means much easier and efficient processing of the RAW image. I am not sure if Arash is saying this exactly but one counter to my choice above might be that if I downsample the 7D image to make it equivalent to the other two, this would average the noise and make the images comparable.

    What is "noise PSD" BTW?

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    Quote Originally Posted by arash_hazeghi View Post
    snip

    On the other hand, with scaling of pixels, cross talk (optical and electrical), read noise, reset noise as well as QE improves so when comparing cameras of different generation the newer camera usually comes out better. Here is a ISO 3200 file from the Nikon D800, which has been processed (poorly because I did not have the RAW file) and down-sampled to 12 Mpixles (native D700/D3 size). I think everyone would agree that it looks better than the output from those cameras... http://www.arihazeghiphotography.com/photos/D800NR.jpg The D800 is a perfect example of Moore's law for image sensors!

    snip
    Very interesting Arash. I wonder when this breaks down if you take it further? In other words I could envision a FF sensor which is massively sampled with very tiny pixels (say the size of a point-and-shoot or smaller), then down-sampled to say 20mp in-camera. Would this be a viable approach to eliminating noise at higher ISOs?

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    Quote Originally Posted by John Chardine View Post
    Roger- Whether is should theoretically or not, in all the images the 7D shows more noise than the 1DIV or 5DII, which seem more or less equivalent (5DII appears slightly better). For me this is a big factor that outweighs the extra detail in the 7D image and is one reason I love my 1DIV and 5DII so much! Less noise for me means much easier and efficient processing of the RAW image. I am not sure if Arash is saying this exactly but one counter to my choice above might be that if I downsample the 7D image to make it equivalent to the other two, this would average the noise and make the images comparable.

    What is "noise PSD" BTW?
    yes that's what I was saying. PSD=Power Spectral Density, it's a measure of noise as a function of spatial frequency. One other complication is that the bi-cubic down-sampling in PS is not a an ideal low-pass filter either.
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    Quote Originally Posted by John Chardine View Post
    Very interesting Arash. I wonder when this breaks down if you take it further? In other words I could envision a FF sensor which is massively sampled with very tiny pixels (say the size of a point-and-shoot or smaller), then down-sampled to say 20mp in-camera. Would this be a viable approach to eliminating noise at higher ISOs?
    The overall SNR is fixed by sensor size, a FF sensor at a given QE collects x number of photons, pixel size is just how you divide those photons into buckets (pixels).

    But yes it is possible to provide a native lower resolution but lower noise output using a high-res sensor. When I was dealing a little bit with CMOS sensors there was this idea of averaging pixels pre-demosaic in a high res sensor to improve per pixel SNR. This would be somewhat the ideal low-pass filter which would give you identical results to a larger pixel sensor in the shot noise limit. Canon did implement this with the s-RAW and m-RAW but instead they used a cheap software method to interpolate the already demosaiced RAW data. the final results were worse than processing the images off line in your computer.

    The idea of "RAW" pixel averaging was abandoned because the electronics didn't have enough bandwidth to perform this function at that time.

    FYI, apparently there is a 40 Mega pixel Nokia phone :O that uses this technique with the right hardware!
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    Roger(or anybody else), can u do the same test( assuming u have all three cameras right now) by putting a teddy bear( or something similar with texture ) at a reasonable distance to simulate 'photographing a duck with 300mm lens from the bank' situation. same iso, SS, lens and aperture please :-)

    One set of test can be properly exposed images. Another set can be underexposed by a stop and then pushed one stop in raw conversion.

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    Quote Originally Posted by Kaustubh Deshpande View Post
    Roger(or anybody else), can u do the same test( assuming u have all three cameras right now) by putting a teddy bear( or something similar with texture ) at a reasonable distance to simulate 'photographing a duck with 300mm lens from the bank' situation. same iso, SS, lens and aperture please :-)

    One set of test can be properly exposed images. Another set can be underexposed by a stop and then pushed one stop in raw conversion.
    in focal length limited situations results are similar to what Roger has already shown above, especially lower ISOs and when you don't have to deal with pattern noise in the shadows.
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    Arash,

    Wouldn't a very high res sensor increase the impact of any color filter array issues (edges, angles, gaps)?

    Here is a ISO 3200 file from the Nikon D800, which has been processed (poorly because I did not have the RAW file) and down-sampled to 12 Mpixles (native D700/D3 size). I think everyone would agree that it looks better than the output from those cameras... http://www.arihazeghiphotography.com/photos/D800NR.jpg The D800 is a perfect example of Moore's law for image sensors!
    Luminance noise is better for the down-sampled D800 shot but color noise is much worse from what I get with my D3 at 3200. IMO.

    Cheers,

    -Michael-

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    Quote Originally Posted by Kaustubh Deshpande View Post
    Roger(or anybody else), can u do the same test( assuming u have all three cameras right now) by putting a teddy bear( or something similar with texture ) at a reasonable distance to simulate 'photographing a duck with 300mm lens from the bank' situation. same iso, SS, lens and aperture please :-)
    And kittens....got to have some kittens too
    Chris


    0 .· ` ' / ·. 100
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    Quote Originally Posted by Michael Gerald-Yamasaki View Post
    Arash,

    Wouldn't a very high res sensor increase the impact of any color filter array issues (edges, angles, gaps)?



    Luminance noise is better for the down-sampled D800 shot but color noise is much worse from what I get with my D3 at 3200. IMO.

    Cheers,

    -Michael-
    You are right. The optical cross talk and aberration from MLA becomes worse with scaled pixels for a given technology generation, the FF slightly drops as well. But usually this falls on the Moore's law trend meaning that advances in semiconductor processing technology between two generations will, at least partially, compensate for these effects.

    several years ago one of the main issues in large sensors was "pixel vignetting" the angle of incidence was too large for pixels located near the border of a FF sensor so they would see less light, there was too much optical leakage too. But today this issue is solved by careful micro-lens design. this is one of the old publications from that time, it's no longer relevant. It's amazing how fast things change...

    http://isl.stanford.edu/groups/elgam...tions/C074.pdf
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    Roger, I'm following John here completely with his analysis of the images regarding the noise. Especially in the high ISO's, the 5D is a clear winner, retaining much more detail than the 1D, while producing less color noise.
    However, wouldn't it be fair to judge detail vs. noise on images that are cropped so as to show the subject in the same size? I can't judge from the images presented how much detail will remain in the images from the full frame camera's when enlarged so as to show the subject in similar size as the 7D. It's the quality of the final image (i.e. cropped until the subject has the size you would want in your frame) that counts. I agree with Aresh that when you want to study the effect of pixel size alone that it would be better to compare equal sized sensors (but even then you don't eliminate other factors that may cause differences in IQ).

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    Quote Originally Posted by arash_hazeghi View Post
    You are right. The optical cross talk and aberration from MLA becomes worse with scaled pixels for a given technology generation, the FF slightly drops as well. But usually this falls on the Moore's law trend meaning that advances in semiconductor processing technology between two generations will, at least partially, compensate for these effects.

    several years ago one of the main issues in large sensors was "pixel vignetting" the angle of incidence was too large for pixels located near the border of a FF sensor so they would see less light, there was too much optical leakage too. But today this issue is solved by careful micro-lens design. this is one of the old publications from that time, it's no longer relevant. It's amazing how fast things change...

    http://isl.stanford.edu/groups/elgam...tions/C074.pdf
    Thanks for the ref... interesting. I would think, too, as pixel size shrinks toward 1-2 microns that just manufacturing tolerances would have an impact (can't map bad cells out either)... reducing the effectiveness of down-sampling for nr.

    Cheers,

    -Michael-

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    Quote Originally Posted by Michael Gerald-Yamasaki View Post
    Thanks for the ref... interesting. I would think, too, as pixel size shrinks toward 1-2 microns that just manufacturing tolerances would have an impact (can't map bad cells out either)... reducing the effectiveness of down-sampling for nr.

    Cheers,

    -Michael-
    Sony showed a 1.25um pixel (on a small sensor) at the IEDM last Dec. good pixel performance but it is somewhat pointless at that size since you start off diffraction limited and yield drops exponentially for larger area....

    checkout this reference, it shows very nice noise measurements etc. I cannot post here due to copyright

    BTW, Sony is the current industry leader in image sensor technology in terms of R&D bandwidth and high profile publications

    Extremely-Low-Noise CMOS Image Sensor with High Saturation Capacity
    K. Itonaga, K. Mizuta, T. Kataoka, M. Yanagita, H. Ikeda, H. Ishiwata, Y. Tanaka,
    T. Wakano, Y. Matoba, T. Oishi, R. Yamamoto, S. Arakawa, J. Komachi, M. Katsumata, S. Watanabe,
    S. Saito, T. Haruta, S. Matsumoto, K. Ohno, T. Ezaki, T. Nagano, and T. Hirayama
    Semiconductor Technology Development Division, Core Device Development Group, R&D Platform,
    Sony Corporation, Kanagawa, Japan. Tel: 81-46-202-4673, Fax: 81-46-230-6170,
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    Quote Originally Posted by arash_hazeghi View Post
    Extremely-Low-Noise CMOS Image Sensor with High Saturation Capacity
    Thanks, Arash. I'll check it out when I get a chance.

    Cheers,

    -Michael-

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    Quote Originally Posted by arash_hazeghi View Post
    For your subject (focal-length limited, high contrast subject, no color detail).....
    To be clear, the Moon as a test target is a very tough subject. There is color in the Moon, and there is a complete range of contrast, from very high (the craters on the terminator, to very low (sunlit areas away from the terminator). Note the subtle color variations in the basalt flows in the maria (the dark areas on the Moon). Note too, how those color differences are lost as ISO increases.


    Quote Originally Posted by arash_hazeghi View Post
    I think a better way is to fix sensor size and just examine pixel size alone (like the 5D3 vs. D800) both receive the same number of photons but just divide them differently.
    But this is no different than my test. Sensor size is irrelevant and the only/main factor changing here is pixel size (and the corresponding small variations in the different generations of the sensors). So for all practical purposes, the sensors could be exactly the same size here. That is why I only specified pixel size in the legends.

    Roger

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    Quote Originally Posted by Roger Clark View Post
    To be clear, the Moon as a test target is a very tough subject. There is color in the Moon, and there is a complete range of contrast, from very high (the craters on the terminator, to very low (sunlit areas away from the terminator). Note the subtle color variations in the basalt flows in the maria (the dark areas on the Moon). Note too, how those color differences are lost as ISO increases.




    But this is no different than my test. Sensor size is irrelevant and the only/main factor changing here is pixel size (and the corresponding small variations in the different generations of the sensors). So for all practical purposes, the sensors could be exactly the same size here. That is why I only specified pixel size in the legends.

    Roger
    moon is a tough subject for sure and you have excelled in photographing it and getting to the bottom of what is best, it is just different compared to birds :)

    I agree since your test was FL limited it doesn't matter how big or small the senor was, the same image was projected on all three sensors and it shows the effect of pixel size only.

    My comment was more in terms "general" comparison between small and large sensors because one of the merits of the large sensor in non FL-limited situations is that you can get closer to your subject and get great IQ-your test is great for the subject and condition described.

    I think the best is a large sensor with a pixel pitch that falls in the sweet spot of current generation technology ;)
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    BPN Viewer Steve Canuel's Avatar
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    Dumb question alert. Is it possible to build a sensor with two different size pixels and if so, would there be any benefits (best of light collecting and detail capturing).

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    Quote Originally Posted by John Chardine View Post
    Roger- Whether is should theoretically or not, in all the images the 7D shows more noise than the 1DIV or 5DII, which seem more or less equivalent (5DII appears slightly better). For me this is a big factor that outweighs the extra detail in the 7D image and is one reason I love my 1DIV and 5DII so much! Less noise for me means much easier and efficient processing of the RAW image. I am not sure if Arash is saying this exactly but one counter to my choice above might be that if I downsample the 7D image to make it equivalent to the other two, this would average the noise and make the images comparable.
    1st, yes one could, with a decent algorithm downsample the 7D image to be closer to the 5DII. At the high end, this will work quite well. In the deep shadows it doesn't quite work becuase of the added read noise in the pixels, which would add up to more noise than that from a single larger pixel.

    But all this is a drift from the intent of the thread. With the Canon 1DX and Nikon D4 we have a choice of very large pixels and with cameras like the 7D and D800, a choice of very small pixels. But for people in focal length limited situations (many bird photographers have this problem), should one buy a larger pixel camera or a smaller pixel camera.

    I didn't give my opinion because I didn't want to bias results for the first day. But here goes. I find your statement that the 5DII produces the best image interesting because I see it differently.

    Here is my assessment:

    In all the images, the 5DII images fail to show the subtle color differences that the 7D and 1D4 show. The color in the 1D4 and 7D are very close (until noise hides it).

    ISO 100: 7D noise is small and detail is well above other images. 7D=top, 2nd=1D4

    ISO 800: 7D noise is showing, but the detail is still well above the other cameras. 7D=top, 2nd=1D4

    ISO1600: 7D noise is becoming prominent, but image detail is still very good. 7D=top, 2nd=1D4, but the difference is narrowing.

    ISO3200: 7D noise is becoming objectionable and color is getting lost, in particular in Mare Serenatatis (the large circular dark area in the upper center). top=1D4, 2nd 7D. I do believe a good downsampling algorithm could improve the 7D to close that of the 1D4.

    ISO6400: Noise is too apparent in 7D, and 5DII (which is slightly older technology than the 7D or 1D4). Top=1D4, 2nd=5DII. In my numerous sensor evaluations, I consistently see the 1D series sensors have fewer hot/bad pixels and the images here show that too: the 7D and 5DII images have a lot of "spiky" noise not seen in the 1D4 image.

    In all the images, if you boost the low level, you will see that all the 7D and 5DII images have a lot of fixed pattern noise, which decreases as ISO increases. The 1D4 has a little fixed pattern noise at low ISO which quickly decreases at intermediate ISOs.

    The bottom line for me: given a focal length limited situation and desire for as much detail as I can get, a camera with small pixels, like the 7D is the way to go. Not shown in the test, but what Arash alluded to: given a non focal length limited situation where you can change position to get the subject to fill the sensor, a larger sensor (e.g. full frame) with the most pixels is the way I would go. But if money were not an object, a compromise pixel size and high quality sensor like in 1D series is the way I would go.

    Personally, with a small improvement in pixel efficiency implied by the latest camera announcements, pixels a little smaller than the 1D4 with the same signal-to-noise ratios as the 1D4 pixels in a full frame sensor would be ideal, something like 5-micron pixels (thus 34.5 megapixels) would be ideal.

    Roger

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    Quote Originally Posted by Roger Clark View Post
    Personally, with a small improvement in pixel efficiency implied by the latest camera announcements, pixels a little smaller than the 1D4 with the same signal-to-noise ratios as the 1D4 pixels in a full frame sensor would be ideal, something like 5-micron pixels (thus 34.5 megapixels) would be ideal.

    Roger
    I agree 5um @ FF is the best in overall IQ for a variety of conditions... let say the maximum bandwidth possible with current generation ASIC is equal to 1DX (14X18=252Mpixel/sec). For action the threshold is about 8fps this would give about 32Mpixls, pretty close to the figure above. So the ideal camera would be ~32 Mpixel FF @ 8fps.

    Just imagine a 32Mpixel 8fps FF body with flagship AF in a compact and rugged body. This would have been such a hit covering from landscape to bird photography....bummer they didn't make it!

    for now we have to just shoot with what we have, maybe next time

    the way it is right now they make you buy at least two bodies so they can profit more...
    Last edited by arash_hazeghi; 03-02-2012 at 10:51 PM.
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    Quote Originally Posted by Jerry van Dijk View Post
    Roger, I'm following John here completely with his analysis of the images regarding the noise. Especially in the high ISO's, the 5D is a clear winner, retaining much more detail than the 1D, while producing less color noise.
    However, wouldn't it be fair to judge detail vs. noise on images that are cropped so as to show the subject in the same size?
    That is a different test and certainly valid. But to do that, one decreases or expands detail, thus the results are also dependent on the algorithm.

    Quote Originally Posted by Jerry van Dijk View Post
    I can't judge from the images presented how much detail will remain in the images from the full frame camera's when enlarged so as to show the subject in similar size as the 7D. It's the quality of the final image (i.e. cropped until the subject has the size you would want in your frame) that counts. I agree with Aresh that when you want to study the effect of pixel size alone that it would be better to compare equal sized sensors (but even then you don't eliminate other factors that may cause differences in IQ).
    As in my response to Arash, the sensor size is irrelevant in this example. All three cameras could well have been full frame sensors. It is purely a test of pixel size and the trade of detail versus noise. Different people will have different opinions on which is better for them. There is no one right answer, much like in the film versus digital wars.

    Roger

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    Quote Originally Posted by arash_hazeghi View Post
    the way it is right now they make you buy at least two bodies and profit more...
    Exactly. And in a an interview of Bill Gates by Barbara Walters, Bill said never produce a perfect product otherwise you can't sell an upgrade (that is a paraphrase, not and exact quote--I would like to fine the real quote). So if Canon or Nikon or Sony ... produced the ideal camera, we would not need to upgrade every couple of years.

    Roger

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    The drawback is if you keep making small incremental improvements and throw away innovation you might as well become like Microsoft itself... or maybe even Kodak at some point
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    Off topic alert.


    Name:  relit_moon_edit2.jpg
Views: 573
Size:  178.4 KB

    Roger, Thought you might find this interesting. Grabbed it from a quicktime movie (& 'shopped it a little). It's from a Visualization Conference paper by David Akers, et al. It uses a method they call image-based relighting. Essentially image stacking where each image has different lighting... here the different lighting is different phases of the moon, using the high contrast edge area from each image.

    See http://graphics.stanford.edu/papers/ib-relighting/

    Cheers,

    -Michael-

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    Quote Originally Posted by Michael Gerald-Yamasaki View Post
    Off topic alert.


    Name:  relit_moon_edit2.jpg
Views: 573
Size:  178.4 KB

    Roger, Thought you might find this interesting. Grabbed it from a quicktime movie (& 'shopped it a little). It's from a Visualization Conference paper by David Akers, et al. It uses a method they call image-based relighting. Essentially image stacking where each image has different lighting... here the different lighting is different phases of the moon, using the high contrast edge area from each image.

    See http://graphics.stanford.edu/papers/ib-relighting/

    Cheers,

    -Michael-
    Is this different than an HDR?

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    Quote Originally Posted by Dan Brown View Post
    Is this different than an HDR?
    Hi Dan
    Yes, because each image must be taken at a different time. A terrestrial analogy would be to start taking images of a landscape at sunrise and continue to take images for several hours and then somehow combine them to maximize the interesting shadow detail. This has been done with the moon for decades (so with film and darkroom methods, which must have been really tough). For a subject like the moon, these days a 3D terrain model is used and shading is added by computing a solar position that is ideal for each location, then drop color on top of that.

    Roger

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    Quote Originally Posted by Dan Brown View Post
    Is this different than an HDR?
    Yeah. The images are taken over the lunar cycle - sickle, waxing, full (not used), waning, sickle - and only the high contrast area (long shadows on the craters) at the transition from light to dark is used from each image for the composite. If I recall correctly 12 shots (phases) were used. Similar to HDR, but it is the movement of the light rather than exposure that differs from shot to shot.

    This was research in 2003.

    Cheers,

    -Michael-

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    Quote Originally Posted by Steve Canuel View Post
    Dumb question alert. Is it possible to build a sensor with two different size pixels and if so, would there be any benefits (best of light collecting and detail capturing).
    Hi Steve,
    It is not a dumb question at all. There is one sensor with large and small pixels. I forgot who (panasonic?). But they have a neutral density filter over the small pixel so it is less sensitive and use it to extend dynamic range. But I suppose one could use it to enhance fine detail, though a new algorithm would have to be designed. Another method which is used on the Mars rovers is multiple sampling. For example take 10 images and because of vibrations each image is slightly misregistered from the others, and use those micro-differences to detect finer detail. Seems to work but I've never tried it myself. In non-focal length limited situations, it is easier to just increase focal length and do a mosaic.

    Roger

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    Thanks for the reply Roger.

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    Attached Images Attached Images
     
    Here is an example of averaging 2x2 pixels. At ISO 6400, the 7D image is looking pretty ratty, but a 2x2 average really cleans things up and produces a very sharp pretty clean image. The detail is close to the 5D mark II, perhaps better in some areas. If the 7D were full frame with 4.3 micron pixels, then the full image would be 46.7 megapixels, and 2x2 averaged would be 11.7 megapixels. (Think of the D800 in this regard.)

    Roger

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    Quote Originally Posted by Roger Clark View Post
    Here is an example of averaging 2x2 pixels. At ISO 6400, the 7D image is looking pretty ratty, but a 2x2 average really cleans things up and produces a very sharp pretty clean image. The detail is close to the 5D mark II, perhaps better in some areas. If the 7D were full frame with 4.3 micron pixels, then the full image would be 46.7 megapixels, and 2x2 averaged would be 11.7 megapixels. (Think of the D800 in this regard.)

    Roger
    It's interesting that the color noise remains, is even more visible in the 2x2 averaged version to my eye. For an image with a more saturated palette it would seem that color noise would continue to pose a problem, particularly if one intends to lift shadows in post-processing. Think of the D800 vs the D4 in this regard.

    Cheers,

    -Michael-

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    Attached Images Attached Images
     
    Quote Originally Posted by Michael Gerald-Yamasaki View Post
    It's interesting that the color noise remains, is even more visible in the 2x2 averaged version to my eye. For an image with a more saturated palette it would seem that color noise would continue to pose a problem, particularly if one intends to lift shadows in post-processing.
    Michael, Color noise is a lower frequency than luminance noise, so 2x2 pixel averages would have lass effect. but even so, I see the color noise much reduced, and significantly lower than the noise from the 5DII. Perhaps what you think is color noise is actual variations on the lunar surface?

    I'm attaching a stretched version of my previously posted image to show the low end. It shows that the noise, both luminance and color is less than that from the 5DII, is one would expect. A 2x2 average of 7D pixels gives an equivalent pixel size of 8.6 microns, so larger than the 5DII pixels, resulting in better signal-to-noise ratios, thus our perception of lower noise.

    Roger
    Last edited by Roger Clark; 03-05-2012 at 09:12 PM.

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    Quote Originally Posted by Roger Clark View Post
    Michael, Color noise is a lower frequency than luminance noise, so 2x2 pixel averages would have lass effect. but even so, I see the color noise much reduced, and significantly lower than the noise from the 5DII. Perhaps what you think is color noise is actual variations on the lunar surface? Roger
    The appearance of the noise in the reduced version to my eye is slightly more saturated while reduced in size. I sampled (PS) a few areas and did see a minor (1%) increase in saturation, but... there may be some spacial contrast differences from the size difference that I'm picking up visually or perhaps imagining.

    Quote Originally Posted by Roger Clark View Post
    I'm attaching a stretched version of my previously posted image to show the low end. It shows that the noise, both luminance and color is less than that from the 5DII, is one would expect. A 2x2 average of 7D pixels gives an equivalent pixel size of 8.6 microns, so larger than the 5DII pixels, resulting in better signal-to-noise ratios, thus our perception of lower noise.
    Noise being what it is, it's difficult to quantify small differences. Mentally interpolating sizes adds to the challenge. To my eye the 5DII 6400 image has less color noise by virtue of being slightly brighter. I'd be happier with a reduction that is done in conjunction with demosaicing rather than after. I can't parse the impact of conversion in relation to sensor pixel size. It would seem that camera profiles in the conversion process are skewing some of the information making it pretty difficult to know what is being compared.

    Cheers,

    -Michael-

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    Quote Originally Posted by Michael Gerald-Yamasaki View Post
    To my eye the 5DII 6400 image has less color noise by virtue of being slightly brighter.
    Good thread and thanks for posting.

    Just as high ISO noise performance is improving with each generation of camera, Dynamic Range and Color are also improving. At low ISO levels the newer cameras similarly outperform earlier models in terms of dynamic range and tonal range.

    As suggested above, even the move to smaller pixels is offset by improved performance and processing.

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    Quote Originally Posted by arash_hazeghi View Post
    I agree since your test was FL limited it doesn't matter how big or small the senor was, the same image was projected on all three sensors and it shows the effect of pixel size only.
    In my experience, I am almost always focal length limited when shooting birds. There are places where this isn't true--ducks in a park or large bird rookeries like the St. Augustine Alligator Farm--but they're uncommon, and in those cases it's easier to go shorter. If choosing between a wild bird kit that's ideal for focal-length limited situations and one that's ideal for non-focal-length limited situations, there's no question in my mind that I want the one designed for focal-length limited situations.

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    Quote Originally Posted by Elliotte Rusty Harold View Post
    In my experience, I am almost always focal length limited when shooting birds. There are places where this isn't true--ducks in a park or large bird rookeries like the St. Augustine Alligator Farm--but they're uncommon, and in those cases it's easier to go shorter. If choosing between a wild bird kit that's ideal for focal-length limited situations and one that's ideal for non-focal-length limited situations, there's no question in my mind that I want the one designed for focal-length limited situations.
    I think you also have to invest in learning approach techniques or travel to places where photography is more productive if you want professional-quality photos. I don't live in Florida or shoot ducks in a park. Sometimes I photograph some really skittish birds but I am not focal length limited most of the time. If you ask the most successful avian photographers they will confirm that bird photography is not focal length limited. Unfortunately beginners think that they can photograph far birds with short lenses by farming pixels, this leads to the terrible IQ images we often see on the forums. IMHO making a general statement that bird photography is "focal length limited" is very misleading and one of the biggest myths/misconceptions on the internet forums.

    There are types of photography that are truly focal length limited like astro-photography and there is nothing you can do about it, but avian photography is not in that category IMO.
    Last edited by arash_hazeghi; 03-24-2012 at 01:28 PM.
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