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Re: mtf and perceived sharpness
| Mike Tyner | 30 Jan 2007 12:48 |
> Well, my question regards how mtf value and perceived sharpness are > related to each other and I´m convinced that this *has* to do with the > science of visual perception. Of course it does. But your thread got hijacked by our resident troll, a so-called engineer who will insist on injecting pea-brained potshots and making the thread about him, rather than you.
Of course the mtf relates to "perceived sharpness". One problem is we don't have a reliable scale - no good way to assign values to "perceived sharpness" or its inverse, "blur," other than indirect measurements of resolution like snellen acuity or logMAR.
You can bet that blur increases as mtf decreases. But mtf is determined using a focused optical system. Most of the problems with human blur involve systems that won't focus properly. Blur can vary from moment-to-moment, present at some distances and not at others. But the MTF is intrinsic and constant, and the blur it contributes is from constant factors, like media transparency and optical aberrations.
-MT
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| Marc Wossner | 30 Jan 2007 09:38 |
> <otisbr...@pa.net> wrote > [quoted text clipped - 5 lines] > > -MT Well, my question regards how mtf value and perceived sharpness are related to each other and I´m convinced that this *has* to do with the science of visual perception.
Marc
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| Mike Tyner | 30 Jan 2007 03:56 |
> This is a detail of technical analylsis -- and > NOT a medical subject. Yes.. like logic and statistics, there's no room for it in your newsgroup.
Lessee... MTF(v) = Mi / M0 ---- Nope, no sci or med or vision anywhere in that.
-MT
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| otisbrown@pa.net | 30 Jan 2007 03:32 |
Some people are a dense as a stone.
M.T.F. is a technical term -- used to qualify photographs and imagining analysis.
It is not a medical term.
Tragically Allen Leiberman has not a clue about any of this.
This is a detail of technical analylsis -- and NOT a medical subject.
Otis
> "otisbr...@pa.net" <otisbr...@pa.net> wrote innews:1170082986.136025.257750@a75g2000cwd.googlegroups.com: > [quoted text clipped - 4 lines] > > Allen |
| A Lieberma | 30 Jan 2007 02:19 |
> Clarification for the reader: Clarification for the reader. Please disregard Otis's postings. He is not in the medical profession and not in any position to give medical advice.
Thanks!
Allen
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| otisbrown@pa.net | 29 Jan 2007 15:03 |
Clarification for the reader:
M.T.F = Modulation Transfer Function.
Otis
> Hi, I´m a bit confused about mtf curves and perceived sharpness > because I found seemingly contradicting statements. Some texts say [quoted text clipped - 7 lines] > Thanks for your input! > Marc |
| Marc Wossner | 29 Jan 2007 13:47 |
Hi, I´m a bit confused about mtf curves and perceived sharpness because I found seemingly contradicting statements. Some texts say that perceived sharpness correlates best with the 50% value of the mtf (where contrast has dropped by half) and others state that the important values for perceived image sharpness are between 0,5 and 2 line pairs per mm at a viewing distance of 13,5 inches. Are those values related to each other (and is it due to my minor knowledge that I do not see that) or are they really in conflict?
Thanks for your input! Marc
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