# Diffraction Limit Discussion Continuation

Started Feb 21, 2014 | Discussions thread
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 Re: Cutting to the chase. In reply to Steen Bay, Feb 25, 2014

Steen Bay wrote:

bobn2 wrote:

Steen Bay wrote:

bobn2 wrote:

Life is too short to bother more with this pointless exchange. The nub of it is simple, you set out to 'prove' a mundane and obvious result using extensive calculations based on made-up numbers. That itself was an exercise in futility. My objection to that kind of bogusly quantitative exercise is that the might convince gullible people that there is something of substance in them, because on the surface they look deep and complex, when all they are is an exercise in numerbation (not even measurebation, because there are no genuine measurements involved). As for the result, yes if the pixel count is so small (we discover, about 200k) then you wont see the effects of diffraction or anything else. Every lens becomes perfect. What a great idea.

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Bob

Also visible on cameras with more than 200k pixels. If someone for example upgraded from 5D to D800 (from 12.7mp to 36mp), then I'm almost sure that he/she would notice that diffraction would start to visibly reduce the resolution (of a good lens, at 100% view) at a larger aperture on D800 than it did on 5D.

Are you sure? How are you sure?

I love the way that you haven't the confidence in your own views just to say you're sure, so you're 'almost sure'. Would you like to quantify your lack of surety? 5%, 10%, 20%? In which units?

OK, then my guess would be that something like a 20% drop in MTF-50 resolution/sharpness would be 'noticeable' or 'clearly visible' at at least 100% view.

Actually I was asking you to quantify your unsurety, not make a spurious estimate of where this border of noticeability is. I had this discussion with someone else about using made-up figures. What is your '20%' figure based on? Does it matter what it's 20% of? Is it 20% regardless of size of viewing size? Is it subject dependent? How does acuity come in? How does image contrast come in? Have you a guess to make about any of those?

The higher the peak resolution is to start with, the more you have to lose to things like diffraction and camera shake. Nothing controversial about that.

That's not how it's put, though is it? And is just as true about excellent lenses. We have regular threads on this forum saying how mFT lenses are the best. Well the downside of that is that they have more to lose - or is it?

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Bob

Wouldn't call it a downside, but you'll have to be a bit more careful and think a bit more about what you are doing if you want to take full advantage of more MPs or a good lens.

I would have thought that goes without saying. Somehow thought, people feel moved to say it about pixel count but not about good lenses.

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Bob

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