Re: test images: screw-in BLB UV box

From: Joe Smigiel ^lt;[email protected]>
Date: 07/10/05-02:27:36 PM Z
Message-id: <>

>>> 07/10/05 1:31 PM >>>
I really am enamored with the very dark navy blue tone I was able to get
in the area that was not covered by negative (i.e., only glass between
UV source and sensitized paper) so am wondering if the Pictorico is the
problem - maybe the 13 watt bulbs just aren't strong enough to penetrate
the substrate or it is my diginet...>>


I took a quick look at the test strips, a couple cyanotype examples and
one of the POPs. I'd suggest to you the UV source is not intense enough
or the exposure times not long enough (although already excessive IMO).
None of the prints appear to reach d max except in the surround even
given your long exposures. I've used Pictorico OHP successfully for
diginegs for both cyanotypes and van dyke brownprints (gum too) and
while it does block some exposure I get more reasonable exposure times
with negatives I suspect are denser than yours. (I'm using a NuArc
26-1K, the sun, or 1000W quartz halogen lamps.) So, I don't think the
OHP is the main culprit. You are using the OHP rather than backlight
film (which does block considerable UV I'm told) when you refer to

Were the cyanotypes solarizing and the POPs bronzing in the shadows as a
result of exposure before you processed them? Those tend to be good
indicators of sufficient exposure with negatives suited for the those
processes. If the cyanotype shadows solarize, the maximum density of
the shadows will then generally match the surround after processing.
Ditto the bronzed POP shadows and surround.

I also doubt your negatives have the proper densities for these two
processes. Among other reasons I'm basing that statement on the POP
image with the wedding hat. The midtones and highlights look pretty
good there but I don't see the nice deep tone anywhere in the shadows.
(POP really needs a dense contrasty negative.) The very dark cyanotype
and the huge jump in apparent tone between 0% net density and the
adjacent step on your digineg step prints indicate this to me as well.
You probably need to adjust your cyanotype curve but that can't be done
properly until the exposure is sufficient for the process. I'd
investigate a different UV exposure source unless your OK with extending
the exposures even further (although now an additional hour will only
gain you 2 steps, and + 3 hours will gain you only 4 steps, etc.).

Received on Sun Jul 10 14:23:53 2005

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