Re: online photograph assessment visual acuity and contrast sensitivity?


Dear Mike,

The term "Visual Acuity" does not necessarily mean an evaluation of a
picture -- which tends to be subjective, given color, light and many
other factors.

Ther is a more restrictive definition in science. And for the human
eye, it means the ability to "resolve" to points of light to
one minute-of-arc.

Thus, in photographic plates in astronomy, the judgment is in
the ability of the photograph to resolve the separation of
stars (as a pratical matter).

Thus in a camera, you should talk about "resolution" in those terms --
in
an objective manner.

The other issues are subjective, and you can not convince a person
that one "shading" is "better" than another -- you just
wind up with endless arguments about which is better.

But enjoy our conversations on this topic.



On Nov 10, 6:19 am, "docm...@xxxxxxxxx" <docm...@xxxxxxxxx> wrote:
I look at quite a few images online as I am an amateur photographer.
One thing I've noticed is that there is a pretty wide range of
abilities in being able to discern the differences between images.

Often people will compare two cameras on the same image.  And when
they do some people can see pretty significant differences and others
seem to be unable to see any difference at all.

In order to help the debates along a little I would like to find a way
to objectively or at least quasi-objectively be able to test the
ability to discern differences between two images.

Here are two that are currently being discussed onwww.dpreview.comin
the sigma forum:http://forums.dpreview.com/forums/readflat.asp?forum=1027&thread=2996...

The images are at:http://www.pbase.com/franklin/image/105711528http://www..pbase.com/franklin/image/105709356

These two images are from cameras with vastly different capabilities
and one would expect there to be differences simply base on the sensor
size, pixel pitch and number of pixels, yet some seem to be unable to
see the difference.  Aside from the blue sky and objects in the very
far background from around the grocery cart next to a car in the
parking lot and further back, the remainder of the pictures shows much
better granularity, edge sharpness and clarity in the latter image
than in the former.  It's not unexpected given the two cameras.  What
puzzles me is why some people seem unable to see these differences.

Is there somewhere online a test that would help objectively assess
the abilities of the participants in the convsersations so that they
could realize their abilities or lack thereof?

thanks,

Mike

.

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