From: Eric Neilsen (e.neilsen@worldnet.att.net)
Date: 09/28/03-06:37:24 PM Z
Nick, What are the other factors in the exposure circle? What RH are you
printing at? What developer? Test strips and density ranges are only
starting points and each change in RH, developer, temp,. all add up.
Eric Neilsen Photography
4101 Commerce Street
Suite 9
Dallas, TX 75226
http://ericneilsenphotography.com
-----Original Message-----
From: Nick Makris [mailto:nick@mcn.org]
Sent: Sunday, September 28, 2003 12:36 PM
To: alt-photo-process-l@sask.usask.ca
Subject: Re: PT/PD density/contrast/definition
Sandy and all, I tried the method of reducing the exposure by half, and
here are the results:
I now have seperation between 15% and 90%.
The blackest black is now not quite black enough.
The print density range was expanded slightly, but as expected, work needs
to be done to bring in the highlights and there is still an indication that
the exposure is too long.
All of this indicates to me (this is a question) that the tonal range of the
sensitiser in lacking, but I have no idea about what to do next. The mix is
currently 5FO, 5PD and 1PT for a small 2"X8" test strip. The PT is supposed
to be adding some contrast to the sensitiser, but the results of the
reduction in the exposure. If I remove the PT it will reduce the contrast
even further.
Which direction does one go when the negative is contrasty and the
sensitiser is using just equal parts of FO & PD? If I make the sensitiser
any less contrasy or reduce the contrast of the negative the print will
surely be useless.
Still confused and in need of helllllppppp.
Many thanks,
Nick
----- Original Message -----
From: Sandy King <mailto:sanking@clemson.edu>
To: alt-photo-process-l@skyway.usask.ca
Sent: Saturday, September 27, 2003 5:43 PM
Subject: Re: PT/PD density/contrast/definition
A few thoughts.
First, the effective printing density range may be greater in the UV than
what you measure with your color analyzer. This is certainly the case in my
work with the pigmented inks of the Epson 2000P on Pictorico where the
difference between measured density range between a Visual and UV reading is
over log 0.30. So it is possible that the effective DR of your negative is
really closer to 2.0 or 2.1 than 1.7.
Second, your note that the dark steps loose separation beginning at about
30% suggests that you have overexposed the negative. When we print we must
expose for the dark values, and then take steps as necessary to control
contrast in the highlights.
In any event the result you describe is consistent with slight over-exposure
and a negative that has too much contrast to handle the sensitizer you used.
Sandy
Ok (BTW, please correct any questionable assumption made herein), I have a
digital step wedge negative with a base density reading of .39 and a
highlight density of 2.2 (being a complete neophyte, I might have these
reversed) which equals a difference of 1.81. As Sandy kindly pointed out
recently, you also have to make an small adjustment which makes this neg
have a density range of approximately 1.7. As has been discussed recently,
1.7 should be a good density for a normal negative when doing PT/PD. Also,
there is good separation between all the steps when viewed and tested for
density on my old color analyzer, now new densitometer.
I used equal amounts of FO (freshly mixed at 27% as I have done many times)
& PD (older) and a single drop of PT (which has rendered the desired color)
for a total of 11 drops on a proper sized image opening. My rough
calculation is .48 drops per square inch of image area on Cranes Platinotype
when using a glass rod.
The resulting test print indicates that I have arrived at nearly the proper
exposure because the highlights have density up to the proper point on the
steps and the highlights have cleared properly. And, the black is as black
as I could ask for.
On the other hand, the dark steps loose separation beginning at 30%.
Ed Stander tested this substrate and found it to have an identical
association between visible and UV light blockage in the entire range - Our
thanks to and a quote from Ed:
"The film blocks a proportion of received UV and Visible light equally
across the board. There are no real peaks or troughs in the transmission
curves. Having said this, the blockage is as follows: The waxed film
blocks 1/2 of the UV falling on it, while the unwaxed film blocks 3/4 of the
UV it receives. These values (amazingly enough) are nearly exact at 360 -
400 nm."
I infer from the above statement that if I use the film unwaxed, I will add
a stop of exposure to my established time plus compensation for the base.
In the case above, the exposure is just more than twice the length of the
exposure for a Lightjet neg that I have printed successfully many times - as
expected.
So, where am I? Well that's what this post is for - I don't have any real
direction to follow here and I'm looking for some input.
Could the ink blockage for the UV not be linear to the visible light (my
enlarger) that I used to test the density?
Could I have miscalculated the density (complete babe in the woods here) and
in reality the neg is more/less contrasty than I'm thinking it is?
Could some of chemicals be outdated? Potasium Oxylate (cold bath) which as
I understand it is better as it gets older (I also tried some unused),
freshly mixed Ferric Oxylate and I can't believe that the EDTA has any
bearing here.
Could the single drop of PT be enough to increase the contrast of the print
from an already ok (read that I'm assuming a proper contrast for PT/PD)
negative?
I'm sure to be embarrassed when the simple answer is arrrived at and I
promise to report.
Appreciate your thoughts,
Nick
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