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09-08-2008, 05:34 AM   #1
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Diffraction issue

Its not Pentax camera/lens test comparison but made me thinking about that more megapixels means less good photos dpreview.com - Lens Review - Fullscreen . Is diffraction which makes the result of the 40D worst than the 5D ?
Thank you.

09-08-2008, 06:42 AM   #2
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there is some kind of calculator here :

Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks
09-08-2008, 09:42 AM   #3
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QuoteOriginally posted by deejjjaaaa Quote
Taking that in consideration the better solution would be 6Mpx for a APS-C sensor and 12Mpx for a full frame sensor.
Why then we see again (lately it was less aggresive) this megapixel war ? It leeds to the fact that you won't be able to use the lens at f:8 beacuse diffraction (with the same results when you used it on a less number of pixels camera).
No, no, I prefer less megapixels, less diffraction and less noise; less , not more.
09-08-2008, 12:08 PM   #4
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Regarding this here is another link Do Sensors “Outresolve” Lenses? which says : "Consider a 35mm system with a lens at f/11. At best, the maximum resolution you will get is equivalent to 16 MP, even if your camera has 22 or 25 MP. In the case of an APS-C based system the limit goes to 7 MP, and 4 MP considering a Four Thirds format. Stopping down to f/22 the limit of the effective resolution of the 35mm based system goes to 4 MP!"

09-08-2008, 12:38 PM   #5
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I am new to digital photography, but I suppose Nyquists law still applies here. Which means that the smallest detail you can accurately reproduce would be 2 pixels wide and/or high. That does not take aliassing etc. into account, so I suppose that whatever the smallest detail your lens system is able to produce, the sensor needs to put 3-4 pixels on it to be able to reproduce it digitally without aliassing distorting it.

In other words, you need mucho pixels
09-09-2008, 10:12 AM   #6
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i dunno, i always think of light as a seemingly infinite amount of waves

all-else-being-equal (and its NOT) the more sensors you have that can record it, the better, because you then you have cropping/zooming ability, and more information to work with so things like colour gradation work better.

if you have 2 pixels in a square foot, gradation from white to black is well.. very plain.

if you have a billion pixel in the same square foot, gradation is much finer

ofcourse... at that point your eyes wont be able to tell between a million and a billion... but its still cool to know that its there
09-09-2008, 10:31 AM   #7
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QuoteOriginally posted by Gooshin Quote
i dunno, i always think of light as a seemingly infinite amount of waves

all-else-being-equal (and its NOT) the more sensors you have that can record it, the better, because you then you have cropping/zooming ability, and more information to work with so things like colour gradation work better.

if you have 2 pixels in a square foot, gradation from white to black is well.. very plain.

if you have a billion pixel in the same square foot, gradation is much finer

ofcourse... at that point your eyes wont be able to tell between a million and a billion... but its still cool to know that its there
If more is better then how the phenomenons from the links above can be explained (less quality for the same image when using the same quality lens at f:8/f:11/f:16 but with camera which have sensors with different density of pixels) ??? see the links , especially the first and the second one.
09-09-2008, 11:27 AM   #8
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because pixel construction is an engineering problem.

if tommorow some company makes pixels that record light from all angles while producing zero heat and no information overflow, and an algorithm that can somehow calculate out interfering rays..

well, you would have one awesome camera.

but again i'm not saying that there IS no limit.. there certainly is a limit, but one we havent quite reached.


ohh and if this sensor would be a concave-half-sphere... we would have some amazing glass varieties for very low cost.


Last edited by Gooshin; 09-09-2008 at 11:39 AM.
09-10-2008, 02:06 PM   #9
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QuoteOriginally posted by montecarlo Quote
Its not Pentax camera/lens test comparison but made me thinking about that more megapixels means less good photos dpreview.com - Lens Review - Fullscreen . Is diffraction which makes the result of the 40D worst than the 5D ?
Thank you.
Same phenomenon dpreview.com - Lens Review - Fullscreen starting with f:8.
50mm f:1.4 lens at f:11 mounted on a FF 12 Mpx camera and than mounted on a APS-C 12Mpx camera. I thought that a crop sensor camera will be in advantage by using the center of the lens. Yes, regarding the vigneting the situation is different but the resolution.
09-10-2008, 02:44 PM   #10
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QuoteOriginally posted by montecarlo Quote
I thought that a crop sensor camera will be in advantage by using the center of the lens.
it will be if you are talking about using it wide open, but who promised you an advantage @ f8 ? typically MTFs are published for the widest aperture.
09-10-2008, 02:56 PM   #11
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QuoteOriginally posted by deejjjaaaa Quote
it will be if you are talking about using it wide open, but who promised you an advantage @ f8 ? typically MTFs are published for the widest aperture.
Yes but I rarely use the lenses wide open. I use f:8 and f:11 (I photograph more street photography) and exactly there the APS-C camera's result looks less good than the full frame's one.
09-10-2008, 06:43 PM   #12
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QuoteOriginally posted by montecarlo Quote
Yes but I rarely use the lenses wide open. I use f:8 and f:11 (I photograph more street photography) and exactly there the APS-C camera's result looks less good than the full frame's one.
then try shooting at F5.6

when you say the FF images are "better", what exactly about them do you consider better?

and what lenses, street photography can be many things.

shooting at F11 on an APS-C camera almost ensures that pretty much everything in view is in focus if your target is a "street" with the focus 20 feet or more in front of you
09-10-2008, 11:12 PM   #13
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QuoteOriginally posted by Gooshin Quote
then try shooting at F5.6

when you say the FF images are "better", what exactly about them do you consider better?

and what lenses, street photography can be many things.

shooting at F11 on an APS-C camera almost ensures that pretty much everything in view is in focus if your target is a "street" with the focus 20 feet or more in front of you
Well, exactly that's why I use f:11 , to have more DOF and f:8 if I need an extra speed for less light (or less f:5.6 for even less light). More, generally a lens reaches it's sweet point at f:8 (not every lens though).
Now, using the same lens on FF and APS-C resulted with different results (at f:8, f:11, f:16, ...) in the benefit of the FF one but I hope on my APS-C 6Mpx sensor of K100D with a pixel density 1.7 MP/ccm is close to the Nikon FF 12 Mpx sensor with 1.4 MP/ccm
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