Diffraction Limit Discussion Continuation

Started 9 months ago | Discussions thread
Great Bustard
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Re: Diffraction Limit Discussion Continuation
In reply to Jonny Boyd, 9 months ago

Jonny Boyd wrote:

It tells you plenty. You have made a universal claim that diffraction always causes peak sharpness at the same aperture, regardless of pixel count. While I agree that that is mathematically correct...

Not merely "mathematically correct", but supported by all the lens (system) tests.

...I also believe that a drop in resolution will in some cases only become noticable at a smaller aperture for a low res sensor than a large one.

When the drop in resolution becomes apparent depends on many factors, not the least of which is how large you display the photo. In any case, we also all agree that the sensor with more pixels will have higher resolution, all else equal.

Thus, since a given lens peaks at a particular aperture regardless of the pixel count of the sensor, and a sensor with more pixels will always resolve more than a sensor with fewer pixels (all else equal), then in what sense does "diffraction limit" have any meaning, or than how Bob characterized it:

http://www.dpreview.com/forums/post/53154169

The 'limit' is just a bogus idea. McHugh has taken a well defined optical term - a 'diffraction limited' system is one so good that diffraction is the only limit on its performance - turned it inside out and made it into something senseless.

That's all I'm claiming.

In what way are sensors with more pixels any more "diffraction limited" than sensors with fewer pixels?  That when viewing at 100% on a computer monitor you can see the resolution fall faster from the peak aperture, even though the peak aperture is the same, regardless of the pixel count, and the sensor with the higher pixel count has greater resolution?

If I can find one instance where numbers demonstrate it, then I am correct.

"A number multiplied by itself is always the same number.  For example, 1x1 = 1."  So because I found a single instance where numbers demonstrate the claim, does that make the claim correct?

Just saying that we have to be careful with language as sloppy language can lead to misinterpretations, just like the term "diffraction limited".

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