|
Science Forum Index » Medicine - Vision Forum » mtf and perceived sharpness
Page 1 of 1
|
| Author |
Message |
| Marc Wossner |
 Posted: Mon Jan 29, 2007 9:47 am |
|
|
|
Guest
|
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 |
|
|
| Back to top |
|
| otisbrown@pa.net |
| Posted: Mon Jan 29, 2007 11:03 am |
|
|
|
Guest
|
Clarification for the reader:
M.T.F = Modulation Transfer Function.
Otis
On Jan 29, 8:47 am, "Marc Wossner" <marc.woss...@gmx.net> wrote:
Quote: 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 |
|
|
| Back to top |
|
| A Lieberma |
| Posted: Mon Jan 29, 2007 10:19 pm |
|
|
|
Guest
|
"otisbrown@pa.net" <otisbrown@pa.net> wrote in
news:1170082986.136025.257750@a75g2000cwd.googlegroups.com:
Quote:
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 |
|
|
| Back to top |
|
| otisbrown@pa.net |
| Posted: Mon Jan 29, 2007 11:32 pm |
|
|
|
Guest
|
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
On Jan 29, 9:19 pm, A Lieberma <liebe...@myself.com> wrote:
Quote: "otisbr...@pa.net" <otisbr...@pa.net> wrote innews:1170082986.136025.257750@a75g2000cwd.googlegroups.com:
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 |
|
|
| Back to top |
|
| Mike Tyner |
| Posted: Mon Jan 29, 2007 11:56 pm |
|
|
|
Guest
|
<otisbrown@pa.net> wrote
Quote: 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 |
|
|
| Back to top |
|
| Marc Wossner |
| Posted: Tue Jan 30, 2007 5:38 am |
|
|
|
Guest
|
On 30 Jan., 04:56, "Mike Tyner" <mty...@mindspring.com> wrote:
Quote: otisbr...@pa.net> wrote
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
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 |
|
|
| Back to top |
|
| Mike Tyner |
| Posted: Tue Jan 30, 2007 8:48 am |
|
|
|
Guest
|
"Marc Wossner" <marc.wossner@gmx.net> wrote
Quote: 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 |
|
|
| Back to top |
|
| Marc Wossner |
| Posted: Wed Jan 31, 2007 5:49 am |
|
|
|
Guest
|
Quote: On 30 Jan., 13:48, "Mike Tyner" <mty...@mindspring.com> wrote:
"Marc Wossner" <marc.woss...@gmx.net> wrote
snip
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.
Yes I know about those problems and that´s why I keep wondering why
the values I stated at the beginning are regarded as important for
perceived sharpness. Maybe they are just picked as samples a lot of
people can agree on but if so no source says it clearly. That´s why I
´m confused.
Marc |
|
|
| Back to top |
|
| |
