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Re: Pt/Pd printing with various lights
Title: Re: Pt/Pd printing with various
lights
Eric,
I am surprised that you find my tests too loose to "prove
anything." If anyone else at anytime has conducted tighter tests
with a several different light sources in platinum, palladium or with
a combination of the two, please tell me where I can see the results.
Typically the information we get about printing with different light
source is purely anecdotal and involves no attempt at all to provided
control parameters. You know how it works. Joe Blow tells us he
changed out his Type A lights for Type B and now is getting two stops
more printing speed and more contrast. But Joe failed to mention that
this was purely subjective evaluation, or that he was using a new film
and/or developer, or that he also changed the ballast, or that he is
now using a new printing frame, or that he decreased the distance from
the frame to the lights, or that the old and very inefficient air
conditioner outside had been replaced with a more energy efficient
unit, or that he really never kept any exposure information at all,
etc.etc.
In any event my tests were done to "find out
something", not to "prove anything." And since I have
clearly outlined the parameters of my testing I don't make any claims
that go beyond the findings.
You have raised two questions about the validity of my testing.
Since I am not an experienced platinum printer I think it appropriate
to discuss each of these questions.
First, you describe the coating as of undetermined in nature.That
is not at all the case. Granted that I did not give the composition of
the coating but I noted that it was Dick Arentz' #7 mixture, the
formula of which is given in his book on Platinum and Palladium
Printing. He describes the AB method of platinum and this particular
mixture is described on p. 60 of his book Platinum and Palladium
Printing as a mixture for printing with medium contrast negatives.
Since Arentz is one of the premier Pt/Pd printers in the world
and this book was published by Focal Press I assumed that this
terminology would have meaning for other Pt/Pd printers even though it
does not for me. It is described as a coating of equal parts of
palladium and platinum designed to print a negative with a DR of
1.35-1.40, a mixture that I would think fairly typical of what many
people use in actual practice.
Second, you questioned the reliability of the results
because coating was done outside of my own working environment and the
testing was not done until a day later. I am sure you are right in
that the speed and contrast of a material will change with time
between coating and exposure and with humidity. This was one of my own
concerns when Dick and I initially discussed running the tests Pt/Pd
tests. However, after discussions with Dick he convinced that this
procedure would not interfere with the reliability of the tests when
the objective was to compare printing speed and contrast with
different light sources. The thinking was that although the speed and
contrast of the samples might indeed be different the change would be
uniform.
I don't have any idea what tests with different mixtures of
platinum and palladium might show. I know from my own tests that the
curves for palladium and platinum are of different shape, even at the
same ES, and there may indeed be a difference in printing speed
with light sources of different wavelength depending on what
particular salt or combination of salts was being used. What I
know is that I tested what appears to be a fairly typical Pd/Pt
mixture with very carefully controlled procedures and found that the
BL tubes were one full stop faster than the SAs in this
test.
Sandy
Sandy,
As platinum and palladium have different response curves, you have
been only able to test an undetermined coating with three different
light sources. I would not make any conclusions about all
platinum/palladium coating based on these test. Since platinum
and palladium are both speed sensitive with regard to humidity, they
indeed have been shown to react to differing wave lengths to produce
different yields, I find your test to be too loose to "prove"
anything beyond that all three react to your lights with equal +/-
results.
EJ
Neilsen
----- Original Message -----
From: Sandy
King
To: alt-photo-process-l@sask.usask.ca
Sent: Wednesday, May 08, 2002 8:14 PM
Subject: Re: Pt/Pd printing with various
lights
Eric,
I agree that if the purpose of my test had been to compare
the absolute speed of different processes it would have been best to
coat, dry, expose and develop all of the samples in my environment.
However, the purpose of these tests was not to determine the
absolute printing speed of the Pt/Pd material vis a vis another
printing process, but its relative speed with different lights.
In that sense I believe that the results of the test are very
reliable. I made three different test prints with each light and
results were almost identical for all three tests made with a specific
light. If any one test had been off with respect to the other two it
would be reasonable to suspect a difference in speed or contrast in
the samples and that would of course have invalidated the test
results. Since this was not the case, however, I am reasonably
certain that these results are valid.
Sandy
Sandy,
I would think that a better test would be to coat them yourself.
Speed changes in paper and contrast may change to much sitting for a
day or more.
----- Original Message -----
From: Sandy
King
To: alt-photo-process-l@sask.usask.ca
Sent: Sunday, May 05, 2002 6:53 PM
Subject: Pt/Pd printing with various lights
A few weeks ago I posted some
preliminary observations on the use of different UV sources with
Pt/Pd. As you may recall I exposed a Stouffer TP 45 step wedge
to paper coated with Dick Arentz' Pt/Pd Mixture #7, using the
following light sources: 1) 20 watt Phillips BL, 2) 20 watt GE BLB, 3)
75 watt URI Super Actinic, and a 1000 watt HID-Mercury
Vapor lamp. Today I read the densities of the tests and plotted curves
with Davis' Plotter program, with the following results.
BL
BLB
SA* HID
Speed Point
2.5
2.4
2.3 2.2
Exposure Scale
1.31 1.36
1.23 1.31
IDMax
1.17 1.20
1.23 1.31
* I also tested the 20-watt Phillips Super Actinic tubes
and the results were virtually identical to that of the 75-watt URI
tubes.
*The HID-Mercury Vapor lamp was tested with a center
filter which reduces printing speed by about two full stops. Without
the center filter this lamp is faster than at least one full stop than
any of the other lights.
For those not familiar with the above terms, here is some
explanation of terminology.
The Speed Point indicates the speed of the material
and is expressed here in relative terms. The higher the number the
faster the printing speed. The values are in log units where each
value of 0.1 represents one-third of a stop, or 0.3 corresponds to one
full stop. Thus, the BL tubes turned out in these tests to be
one-third of a stop faster than the BLB tubes, two-thirds of a stop
faster than the SA tubes, and one full stop faster than the
HID-Mercury Vapor lamp (with the center filter).
Exposure Scale is the range between the minimum and
maximum density values required to print all of the tonal values. It
is also expressed in log values, with each 0.3 units corresponding to
one stop. An ES of 1.3, for example, corresponds to 4 1/3 stops. ES
relates to image contrast, the lower the number the higher the
contrast.
IDMax is the value that corresponds to 90% of maximum
black.
There have been quite a number of claims that Super
Actinic tubes are faster than BL and BLB tubes for printing in
platinum. My tests show the opposite. However, the SA tubes did
produce images with more contrast than any of the other lights.
Just for the record I ran the tests three times and the
results were very consistent. Over 95% of all readings of the three
tests made with a specific light source were identical, and no
difference greater than log 0.02 was observed.
Comments and questions about these tests are welcome.
Sandy King
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