Re: physiology vs. sensitometry

Pollmeier Klaus (100561.2417@CompuServe.COM)
16 Jun 96 18:59:41 EDT

Terry wrote: <Is it not possible that if our perception of d max is different
from the
sensitometer's mechanical record, that our perception of intermediate tones
might also be different such that we may be able to perceive as many tones in
1.4 on platinum as we can in 2.0 on silver gelatine.>

Definitely not. The perception of Dmax' deepness may be influenced by one's
subjective brain but the separation of tones depends on your eye's objective
ability to notice the difference. So if your eye physically needs, let's say, a
minimum difference of 0.01 logD to separate one tone from the next, you can see
200 different tonal values in a 2.0 print and 140 in the 1.4 print. But of
course, you (and most of us) may perceice these tones as "richer" than the two
hundred... Or had anyone on this list ever counted tones?

BTW: During the last days I tried to watch high contrast scenes to see wether I
loose separation in the shadows when viewing the highlights. I noticed that I
didn't perceive shadow detail at the very first glance, but as soon as I watched
the scene a little longer (still carefully not focussing on the shadows), I
noticed detail even in very dark parts. Maybe the first effect is caused by the
brain giving bright things a priority of perception and allowing the darker
parts to take some place in our thoughts after the highlight analysis is
complete. This way perception of dark tones would be a question of time. That I
could notice detail in the shadows although not focussing on them (hopefully)
makes sense, as those light sensitive elements in our eyes sitting next to the
center of the retina are more sensitive than those in the middle. Probably there
are still other physiological phenomena working but the above could mean, that a
platinum print would better represent a scene that we caught a glimpse of and
that a silver print would be more suitable for a scene that needed long time
viewing?? If that would be the "rule", it would explain why many prints become
interesting when working against the rule... (Yes, let's keep it complicated
;-))

1:00 a.m. now. Late enough.

Klaus Pollmeier