Diffraction Limit Discussion Continuation

Started Feb 21, 2014 | Discussions thread
bobn2 Forum Pro • Posts: 58,097
Re: Diffraction Limit Discussion Continuation

Ulric wrote:

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, I also believe that a drop in resolution will in some cases only become noticable at a smaller aperture for a low res sensor thanma large one. That's all I'm claiming. If I can find one instance where numbers demonstrate it, then I am correct.

With no official standard for what diffraction limit means, anyone is free to come up with one that fits the desired result. Some of those definitions will be more useful than others. You and bobn2 have different definitions and will never be able to agree who is right.

No-one is 'right' - so long as someone defines what they say, then they can say what they mean.

For the record, this is the same thing as when people argue over equivalence using different equivalence relation.

I do have an argument over the whole McHugh 'diffraction limit' definition. My arguments are:

i) I can't see anything that would sensibly be called a 'limit'.

ii) A 'limit' that occurs at different magnifications for different cameras doesn't seem much use.

iii) Even if it were well founded and clearly demonstrable, it obviously has not been well articulated, since very many people on reading McHugh's site and discussions arising from it come away with the impression that high MP cameras give worse results than low MP cameras at small apertures, due to this diffraction limit. It is a common confusion, caused in no small part by that site and people who promulgate this bogus 'diffraction limit' idea. For instance, but one example:


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