the color workflow: scanning/levels/curves and C41
the color workflow: scanning/levels/curves and C41
- Subject: the color workflow: scanning/levels/curves and C41
- From: Robert Wright <email@hidden>
- Date: Sat, 28 Apr 2001 20:30:14 -0400
What are the effects of altering the contrast of color images in photoshop
to account for exposure or lighting contrast issues? Here I am thinking of
the comparison between tradtional black and white controls vs. traditional
color controls. In the wet darkroom, I change paper grades to allow for
exposure variations in negatives, so that a full range of tones can be
produced from each negative.
With c-prints, I have limited contrast controls, ie; portra, supra, ultra
papers to account for exposure differences (I'm ignoring purely aesthetic
choices for the moment) in color negatives. Accurate color reproduction
depends on accurate exposure, although in practice with color negative we
tend to let this slide becuase we think of color neg. as being "forgiving".
These questions have come up in the context of printing a series of interior
photographs where I was mixing flash and fluorescent ambient light. With
c-prints it was relatively easy to match the color reproduction across a
series of negatives, even though my exposure was not consistent. The better
my exposure, the better the print. There were some negatives that were a
little thin, and these of course printed flatter or darker. But overall,
each photograph appeared to have been taken under the same lighting and
shared similar color characteristics.
Photoshop presents me with the opportunity to fine tune the output contrast
of each of these negatives. The surprise (not exactly) for me was how
altering the contrast in curves resulted in a wide range in the repoduced
color. Specifically, flash/ambient crossovers were magnified and the color
control became a kind of riot. It became very difficult to make a series of
prints that shared similar color characteristics once I had done the basic
levels adjustment to account for exposure. The originals were all scanned
at the same time on a kodak photo cd with no tweaking by the operator or the
software.
So where is my question?
Does it make sense to alter the contrast of (properly scanned) negatives in
photoshop to account for exposure differences as we do in black and white,
or does this adjustment corrupt the natural relation of colors in c-41
repoduction?
I understand that c-41/r4a is not "natural" but rather is a system of
reproduction that has become commonplace. But there is something about the
"palette" of c41/r4a that we acknowlege as real.
Should I be applying the same levels adjustment to each negative, or the
best (ie; optimized in the historgram) levels adjustment to each negative in
a group?
What is the "natural" and or "native" color output (gamma?) of c-41
negative materials? Does this have any meaning? Can it be applied to the
levels historgrams?
Are there other controls like HSB which could work better? That is optimize
contrast and brightness without altering the relationship of the colors.
I understand there are a myriad of issues here, one of which is vocabulary
which I hope you can bear with. I have read many of the photoshop "bibles"
and they all take you through the basic levels adjustments and curves. But
there seems to some flaw in this workflow that I can't understand yet.
I am a editorial magazine photographer and i am preparing images not for
press but for portfolio and as finished prints.
I would appeciate any links people have in their favourites menu to where I
could read about this, and thoughts in general.