Re: son of a gum tonal inversion test

From: Joe Smigiel ^lt;jsmigiel@kvcc.edu>
Date: 12/07/05-10:21:13 AM Z
Message-id: <s396c5b7.096@gwgate.kvcc.edu>

Oops. The density of the numbers appears to be about that of step 4 or
5, not step 1. And the printed tone from step 5 does appear to match
the printed tone of the numbers. So it appears the numbers are matching
the highlight threshold value after all and not a darker value from a
less dense portion of the step wedge as I had erroniously assumed
without actually looking at it. The apparent contrast difference here
is part perceptual rather than strictly related to density. It is a
simultaneous contrast effect. The juxtaposition of a light gray next to
a substantially darker printed value is making the tone look much
lighter than it would if we could isolate it.

Coincidentally, the transmission density of the numbers just happens to
match the transmission density of the threshold highlight step on this
particular test exposed for the optimum scale of the paper/gum mix. On
the other, overexposed tests, the numbers also match the value printed
from step 5, only in those tests maximum printed density has been
reached there and the numbers are actually darker as a result of
overexposure.

Makes total sense now.

Sorry...

Joe

>>> Joe Smigiel 12/07/05 12:05 AM >>>
>>> zphoto@montana.net 12/06/05 10:40 PM >>>
>>Why on EARTH your numbers that should be black are white...I'm gonna
guess
that you had enough exposure to keep the pigment from sinking into the
paper
but not enough to have any of the stuff stay on during development.
chris <<

Chris,

Ahhh, but the numbers on the wedge have the same density as step #1 and
therefore should print at the maximum value. Also, since some pigment
is being trapped where the circles are, the surrounded area would tend
to be anchored to it, assuming it received the maximum exposure that it
did. If the circles were totally white the numbers would be more like
islands and might not be anchored as well.

This effect makes absolutely no sense to me.

Joe
Received on Wed Dec 7 10:22:12 2005

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