Diffraction Limit Discussion Continuation

Started Feb 21, 2014 | Discussions thread
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Re: Diffraction Limit Discussion Continuation

Jonny Boyd wrote:

bobn2 wrote:

Jonny Boyd wrote:

bobn2 wrote:

I think that the semantic argument that this discussion tends to end up in (maybe when the 'peak aperture shifts' people realise that they are wrong) is missing the point of the misinformation and damage to practice that this meme causes. Whatever they wish to decide that they really meant in this abstruse semantic discussion, there are many photographers who look at sites such as CiC, and posts here inspired by it, and end up believing that a low pixel count camera will give them sharper results at small apertures than will a high pixel count camera (absurdities like 'D800 unusable above f/5.6'). While I'm quite prepared to believe that wasn't what they really meant, I'd be more impressed had they made that point in the original posts where they claimed there was a 'diffraction limit'.

I don't recall anyone saying that a low pixel count camera will be sharper than a high res camera (if by sharpness you mean overall image detail).

maybe that hasn't been said explicitly (can't be bothered to go through the whole thread to search) but undoubtedly that is how this bogus 'diffraction limit' gets understood.

The diffraction limit exists, it's just not well understood.

Please define what you mean by "diffraction limit". For reference:


Notice also there is no defined 'limit' where the resolution suddenly falls due to diffraction, it is a smooth and even drop-off. 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.

In fact I recall plenty of instances where people have affirmed that although diffraction is visible earlier in high pixel count cameras, they still have more overall detail than a low pixel count camera. What you're saying sounds more like misinformation by suggesting that anyone is making that claim.

I'm basing on what I see understood by it. If we all agree that you still get more detail, what is the point of worrying about this 'diffraction limit' at all?

I don't worry about it personally. But someone asked a question and I found it interesting to think and write about.

It is a genuine concern for those working with telescopes and microscopes more so than ordinary photographers.

The way I see it is that other sources of blur are usually of considerable more importance than diffraction.  The main reason to consider diffraction is to avoid stopping down unnecessarily, such as shooting a landscape at f/16 when everything is easily within the DOF at f/8.

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