sony nex 7 or nikon d7000

Started Dec 21, 2011 | Discussions thread
antoineb
Veteran MemberPosts: 5,307Gear list
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but f8 really IS too small an aperture
In reply to creeker, Mar 14, 2012

I understand why DP Review would want to use f8: depth of field being one, and also the fact that non-exceptional lenses have various issues if not stopped down.

However I question this:

(1) DP Review assume that DIFFRACTION will not be an issue.
This USED TO be correct when sensors were say 6mp.

Indeed theoretical work has shown that at f8, on APS-C, a mere 13mp is enough for the sensor to outresolve a "ideal" lens for yellow-green light. When you sensor is a good deal higher than 13mp you want to stay clear from f8. Even at f5.6 the limit is just 27mp.

So I stick by what I said: (1) diffraction really IS an issue with current sensors, and so (2) DP Review should certainly not go to smaller apertures than f5.6, possibly even just f4. IF they want their results to be meaningful when comparing image quality including noise.

(2) you state that "testing has shown" that diffraction was not a problem.

To prove this, we'd need to see at least two series of test shots, say one done at f8, and another done a f5.6 or f4. Or maybe all three.

Maybe the series at f4, especially if done with a lens that's better than a f3.5-5.6, kit, will make it clear how diffraction is affecting the series done at f8.

I haven't seen any such testing from DP Review - but if it has been done, please post the link I would love to examine the results.

BOTTOM-LINE: given that current sensors already outresolve "ideal" lenses by quite a margin at f8, and given that sensor resolution continues to go up, it is high time that DP Review modify their testing procedures and shoot at f5.6 or better f4.

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