Diffraction Limit Discussion Continuation

Started Feb 21, 2014 | Discussions thread
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Jonny Boyd Forum Member • Posts: 89
Re: Cutting to the chase.

)Just another Canon shooter wrote:

Jonny Boyd wrote:

Just another Canon shooter wrote:

You will not notice much difference if you open up more, either. All this based on you idea that a 5% drop from, say, 1200 is the same, visually, as 5% drop from 2400, which is a very bold assumption and flat out wrong at moderate viewing sizes.

And where exactly is that assumption?

You are applying 5% threshold for low density sensors and for higher one. This does no prove existence of a limit but let us play that game for a moment. Why fixed percentage? Why not measure it absolute terms? Why not on a log scale?

In this post (Re: Diffraction Limit Discussion Continuation) I said:

If we said that a resolution difference of 0.1% was the limit of perception, then for all practical purposes, peak resolution is indeed a plateau that stretches over several apertures for smaller sensor sizes.

That was just to illustrate a point, rather than an attempt to establish where the actual limit lies.

Elsewhere, in this post (Re: Diffraction Limit Discussion Continuation) I said:

We now need a cut-off point for when a change in resolution will be noticeable. If we assume that a 5% change in resolution is noticeable i.e. when resolution drops below 95% of peak resolution, a difference is noticeable, then we see that diffraction only starts to limit the perceived quality of a print at smaller apertures for lower res sensors.

s = 1, 3, or 10 are never perceptibly limited by diffraction; s = 30 is limited at f/22; s = 100 at f/11; s = 300, 1000, 3000 at f/8.

Again, this is for a purely theoretical setup so real world examples of sensors, lenses, and printers may have more or less pronounced behaviour, depending on actual resolution. My model also assumes that the percentage drop in relative resolution that becomes noticeable would be the same for every absolute resolution. It may be that at higher absolute resolutions a change in relative resolution would be noticeable at a higher or lower resolution. I'm not sure about that one.

Again, it was just giving an example of where the change in perceived resolution could be. It wasn't intended to be a hard and fast claim that our eyes will only notice a drop in resolution of 5%. Not were any claims I was making dependent on that figure.

That hopefully would have been clear in the more recent post (Re: Cutting to the chase.) where I used no numbers and demonstrated that both absolute and relative drop in resolution is less for lower resolution sensors. Hopefully it should be clear from that post, that the claim I'm making about there being a point where resolution is sufficiently low for no change in resolution to be noticed when stopping, is a claim that is not built on any assumptions about the point at which the human eye is unable to see a change in resolution. The only assumption is that such a point exists.

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