A few words on Equivalence and comparing systems

Started Apr 2, 2013 | Discussions thread
69chevy
Senior MemberPosts: 1,371
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Re: No you did not, or ...
In reply to Great Bustard, Apr 3, 2013

Great Bustard wrote:

Sorry, but that's all incorrect.  Again:

http://www.josephjamesphotography.com/equivalence/#diffraction

In short, diffraction softening is a result of the proportion of the photo that the Airy Disk spans, and that proportion is the same for all systems at the same DOF, regardless of sensor size or pixel count.

Also, the airy disc size only stays proportional when the relative size of the fstop is also in proportion.

In your scenario, you give the smaller sensors the same size entrance pupil, which means the same size airy disc, which means more apparent diffraction for a smaller sensor with higher pixel density.

The airy disc blurs more pixels in your equivalent scenaio, so diffraction is very different (not equivalent).

I'm not wrong on this, I promise.

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