Re: How to apply curves in PS for digital negatives...

Date: 11/30/05-01:29:05 AM Z
Message-id: <>

I'm still visiting my sister in Connecticut, but have been following this
thread the best I can and thought I would comment on a number of posts in one
swell foop.

I agree with Dan's comment that it really does not matter whether you apply a
curve to the positive image file or the "negative" image file—as long as you
are consistent and apply the curve to the version of the image it was built
for. I prefer to build my curves and apply them to the negative image because
my little pea brain finds it easier to think in terms of negative density and
how it needs to be modified.

Judy is correct that you don't want to confuse the purpose of a step tablet
(or sensitivity guide if you are New Age) made with an inkjet printer with that
of a standardized film test tablet such as those made by Stouffer. They
serve very different purposes. You can create a steptablet on an inkjet printer
that will have the same UV step densities that a Stouffer gives, but it would
be very specific to the printer, inkset, alt process and contrast mix, etc etc's just a lot easier to buy one of those little devils and use it.

Curves all do pretty much the same thing and will in most cases have pretty
much the same general shape, depending on whether they are built to apply to
the positive image or the negative image. They are, however, very specific to
the individuals workflow, printer, inkset, etc.

If you match the density range of the digital negative to the exposure scale
of the alt process before you build the curve, you have won half the battle.
Then the curve doesn't also have to adjust for a mismatch of exposure scale
and density range. Then you really see what the curve is meant to do, adjust
the relative tonalities of the final print to look the way you want it—that
may be, in the case of a curve that "straightlines" the tones, give you a print
that matches what you see on the monitor. Or you may wish to vary from that.
  Currently, my thinking is that there are two families of curves that can be
used to build a digital negative, the Straightline Curves as described above
and another family that mimics what one would get printing an in-camera
negative. This latter is somewhat of a generalization, because how the alt process
would print would depend on the film used and the manner of development used
to create the in-camera negative. However, it is quite simple to even mimic
the favorite film/developer combination.

This past year I have changed my workflow such that I am using either one of
the two types of curves mentioned above, or, more often, a hybrid of the two
types of curves.

Ignore the following if you are disgusted by shameless, self serving plugs.

Currently I am testing a new piece of stand alone software that I have
written (Curve Calculator II) that allows one to do the above types of curves quite
easily and efficiently... CCII calculates your curve automatically from your
data, gives you a preview of how the hybrid curve will print with the alt
process you are using—then you just click a button and export the curve in a
Photoshop Curves file. After testing these different types of curves, I decided I
wanted to be able to build a curve for specific images. So, by looking at
the image, I can pretty well predict which curve I want to use, build it & be
using the curve in less than a minute.

When I return home, I plan to use this software to compare how some of the
different variables such as humidity, paper, contrast mix, etc actually affect
the final curve, since the software allows such comparisons across calibration

End of Shameless Self Promotion, you can now uncover your eyes....

I also agree that most folks out there work hard to develop their own
workflow and if it works for them, then that's all you can ask for. I'm just lazy
and I like a workflow that is really predictable for me. I hate wasting the
time it takes to make a print, only to find out that it sucks.

By the way, I spent a great day at the Florence Griswald museum in Old Lyme,
CT looking at work by American Impressionists along with a great exhibition of
platinum prints from the same period (and of the same landscapes) by the
Allen Sisters. My sister thinks the Allen Sisters might be on to something with
this pictorialist, platinum printing thing. Looking forward to seeing Carl
Weese's show in Washington, CT soon! Jane says hi!

Best Wishes,
Mark Nelson
Precision Digital Negatives
Received on Wed Nov 30 01:29:53 2005

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