From: Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Date: 05/17/00-06:16:21 AM Z
Nick Makris wrote:
> ... Not having a sensitometer, I'm not able to
> provide any specifics.
A densitomiter will NOT provide you with the information you need.
> ... They appear to clear almost immediately after
> entering the EDTA bath....
However, do check the procedure with a clearing test (also using the
indicator) as what may appear to be clear may not.
> ... Is it possible to have a neg that has a contrast range too great to print
> with PD & FO???? ...
Yes, and Eric has mentioned several good points (one follows).
Eric Neilsen wrote:
> ... Don't confuse density range with the shape of the curve. ...
> I have not tried to print just for the shadows with my
> current chemicals although recall that I was able to print those details on
> RC paper.
Do not try to think that a gelatin silver paper will look at more of the
negative than a Pt/Pd coating. The facts are that Pt/Pd coatings do
depend on a greater range of information in the negative. The toe is
not that important as it's values will be merged into black mostly due
to the surface characteristics of the print. However, the straight-line
portion and shoulder are almost entirely used. Although most film can
produce a density beyond that necessary to print pure white in Pt/Pd.
Nick Makris wrote:
> ... I may be expecting more than the process is capable of....
Or you may not be working within the restrictions of the process. This
is different from expectations.
> ... Eric - I am very interested in your suggestions regarding temperature and
> the mixing of PT & PD to control contrast....
The change of temperature of potassium oxalate influences color more
than contrast (slightly lower contrast for a much warmer color). Most
contrast control is used to increase contrast, making it desirable to
get a negative without too much contrast from the start.
> PS After preparing this post, I realized that I do have a densitometer of
> sorts (Photoshop).
WRONG, even though the dropper (densitomiter) of Photoshop is very
useful, it does not tell you how much ink will be deposited and thus the
resulting negative density. One must calibrate for their own output
device and materials. Also the increments in Photoshop are not in a
linear relationship with the output densities. This can be controlled
and calibrated to one's personal preference within the inherent
restrictions, but is only valid for that one set of conditions.
> ... At some point
> during the conversion to TIF, the range changed
The range (or RGB values) can change with a Photoshop mode change,
saving to file (some file types may even differ), coversions when
opening a file, or changed by the printer (or other device) driver. A
fix for this is to make sure all Photoshop settings and devices are set
to the same color management (such as sRGB). And even so, Photoshop may
try to change things anyway.
Finally,
Nick Makris wrote:
> ... I also have recently printed a 21 step negative which didn't provide any
> enlightenment - it printed just fine. Once again, I have no densitometry so
> I am unable to compare the steps to the areas in question.
Have you looked at Chapter 3 of my Guide yet? Making the matrix will
take some of your time and some materials, but it is very much worth
it. The experience and training obtained through this exercise can only
be equaled through years of printmaking. One can learn the relationship
between seeing, negative values, and print values for the materials
selected. One can understand the abilities and limitations of
particular materials and processes. With that knowledge at hand, one
can then begin to make a negative (analog or digital) to use with a
given process.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
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