[quote name='Brightcolours' timestamp='1288614014' post='3864']
Not true. Same aperture, same field of view, SAME DOF.
Aperture is measured in mm's. f-values are focal length divided by aperture.
[/quote]
Ah, yeah, now we're splitting hairs, are we? I meant to say f-stop. DoF depends on reproduction ratio and f-stop. APS-C has a smaller sensor, ergo smaller reproduction ratio for the same composition, ergo more DoF.
Quote:Your proposition is a bit strange: One chooses an aperture to get the desired DOF. One does not choose an f-value just to take it as "standard across sensor sizes".
Well, the problem is that if you want shallow DoF, at some point you're wide open, and as far as I can tell, nobody has made a 35/1.0 APS-C lens at a reasonable price to match the shallow DoF capabilities of a 50/1.4 FF, or a 60/1.0 APS-C to match a 85/1.4 FF. Now what's strange about that?
[quote name='wim' timestamp='1288629132' post='3889']
Nope. Diffraction limits for APS-C are around F/13...
[/quote]
f/13? Have a look at the photozone MTF data for any truly excellent lens on APS-C, and you'll notice that sharpness mostly drops already at f/8 on a 10 MP DX camera...
[quote name='wim' timestamp='1288615327' post='3866']
I said 17-40L on FF is better than 10-22 on APS-C[/quote]
If Photozone is the only lens testing website in cyberspace, I am inclined to believe the performance of the 17-40 f/4L on FF is totally UNDERwhelming when compared to 10-22 on APS-C. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/tongue.gif' class='bbc_emoticon' alt='B)' />
Fortunately, there are [url="http://bit.ly/cU3ozW"]other websites[/url] that prove otherwise. In fact, I'll say that strictly from a resolution point of view, the performance of 17-40 on FF is similar to 10-22 on APS-C.
[quote name='wim' timestamp='1288615327' post='3866']
BTW, try shooting a 10-22 with high contrast conditions, do the same with 17-40L, and tell me what you see ... You might be amazed.[/quote]
Do you have a picture to demonstrate this? I am not clear which aspect you are referring to.
[quote name='wim' timestamp='1288629132' post='3889']
This is actually an opinion, not truth. The guys who wrote this article have been proven wrong by others who weren't as publicized as these guys. If this stuff really was true, we would have seen exactly the same effects with film. Why did we never hear about this? Furthermore CoC and Airy disk are directly related, if not the same. it actually goes a little too far for me to have a discussion about this here, so I want to leave it at that, if you don't mind too much.
[/quote]
Hi Wim,
the reference for my statements were:
http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm and mostly:
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
The cornerstone of their statement, which compares the size of the airy disk (diffraction pattern) with pixel size of the sensor came logical to me. Because if the pixel size is smaller than the airy disk, then the diffused photons will be collected by the neighbour pixel, which might alter the real image because of the color recognition concept of the bayer filter. Can this be a problem also for the film?
The amount and cause of diffraction is based on the size of the entrance pupil, that's a fact. But beyond that, I'm trying to understand the effects of diffraction on IQ given that sensors might have different pixel sizes and areas. If you think that this is not the place to discuss this, please send me the links you have so that I can read and learn.
PS: Thanks for the correction regarding the macro comparison.
Kind regards,
Serkan
[quote name='PuxaVida' timestamp='1288684930' post='3904']
The cornerstone of their statement, which compares the size of the airy disk (diffraction pattern) with pixel size of the sensor came logical to me. Because if the pixel size is smaller than the airy disk, then the diffused photons will be collected by the neighbour pixel, which might alter the real image because of the color recognition concept of the bayer filter. Can this be a problem also for the film?
[/quote]
The best test for all these theories is simply to carry out controlled testing on two cameras and see what you get. There were all kinds of theories on diffraction that got me worried when I bought the 7D. So, I mount the same lens (17-55 f/2.8 IS) on my 12 MP 450D and 18 MP 7D. Made use of tripod, manual focus under live view, cable release, identical exposure etc etc etc. And the result? I can pixelpeep for all I want, but there is no significant difference in terms of diffraction effects from f/2.8 to f/11 between the 450D and 7D. 7D images do not appear any worse than those from 450D at f/11.
My conclusion? To hell with all those armchair theorists and their flawed postulates! The end result, i.e., the images, is what counts.
On a slightly different but related note, [url="http://www.juzaphoto.com/eng/articles/canon_7d_review.htm"]Juza[/url] has direct comparisons between the APS-C 7D and FF 1Ds3. This is what he says:
"When the 7D has been announced, I was doubtful about its image quality at high ISO... Surprisingly, the 7D is relatively good in this aspect. It is not as good as the 1DsIII, but the difference is small - I'd say about 0.5 stop - and it is a bit better than the 500D and 50D.... In this test, I have compared 1DsIII, 7D and 500D from ISO 100 to 12800. The images are 100% crops from the unprocessed RAW file...
The dynamic range is about the same. The 7D seems to capture slightly more detail into highlights (even though it shows a slight magenta cast), while the 1DsIII captures a bit more detail in the shadows - but the differences are so small that in practice you won't see any real difference."
And he backs up his statements with pictures from controlled tests. No armchair theories here.
IMHO, FF offers three advantages over APS-C: shallow depth of field, less demanding on lenses and slightly (not even one stop) better high ISO performance. Dynamic range is NOT one of them. That has been the case since the 5D days and it has not changed.
bryan conner
Unregistered
good grief.....my head is hurting....
Mostly I agree with you... In fact, I'd like to make this kind of test for D300 and D700, since there are no major differences effecting the IQ except for the sensor and pixel size (same metering sensor, both have 14 bit A/D convertion, both allow uncompressed data production etc...). So, this would show meaningful differences concerning the topic we discuss here (sensor area & pixel size), if there are any.
OTOH, I believe that, theory vs. praxis is the wrong way to criticise the discussion here. Rather than that "theory with praxis", so that the statements and arguements can be objective and concrete. Because the IQ is always subjective in the end (my eyes, my LCD screen, my color conception, my noise tolerance etc...), and thus must be supported with the theory.
Kind regards,
Serkan
[quote name='Bryan Conner' timestamp='1288691894' post='3909']
good grief.....my head is hurting....
[/quote]
The easy solution is to just skip these parts.
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[quote name='thw' timestamp='1288691107' post='3908']
The best test for all these theories is simply to carry out controlled testing on two cameras and see what you get.[/quote]
At this point I'll throw a link to a practical test I did before on the Canon 50D only. I was doing a quick test to see the practical impacts of varying aperture balancing DoF and diffraction. See here. It was at low magnification though, only 0.8x and I don't have a bigger sensor camera to repeat it with at the moment. But the main point to take away is diffraction isn't a knife edge effect, but a very gradual one, so I have no issue working in the diffraction region as long as I don't go too far in.
Returning to the thread topic of comparing effects of sensor size, a similar direct comparison between a 5D and 450D would be interesting. Might be hard since I don't own one any more.
The only problem when you don't have the kit to perform tests experimentally is you have to revert back to theory application. If done correctly there's no problem but to me there's always that bit of a reality gap of knowing something and seeing it.
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
Can you please check (if you still have the images on your hard drive), whether the diffraction kicks @ F11-16 also on the left & right edges as in the image centre?... Of course effects of field curvature or decentering must be eliminated. The lens you had used is a decent macro lens and I suppose these effects could be negligable, right?
I really would like to see the results of such a test for D300 and D700, but I could not find it on the net.
Kind Regards,
Serkan
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