Brian Ellis (beellis@gte.net)
Mon, 22 Feb 1999 07:48:14 -0500
Hi Chris - I use a variable contrast cold light head (the Aristo VCL 4500) ato
make enlarged negatives and have never encountered the problem you're having.
I've used it with APH, Aristatone, a duplicating film sold by Photo Warehouse,
and probably other films that I don't now recall. I don't use pyro. I'm
wondering why you're using green light only and whether that might be a source
of the problem. I usually set the contrast to about 5.0, which gives green
plus a lot of blue light. I do this primarily just to get as much light on the
film as possible, thus shortening exposure times, but maybe it inadvertently
has kept me from having the problem you're having. Anyhow, it should be easy
enough for you to dial in a high contrast on your head and see what happens. If
there is a reason why you think it is best to use green light only, I'd like to
know. Brian
Chris Stone wrote:
> Carl,
> I suspect you're right about the mismatch between the tubes and the
> film. The grid marks didn't appear when I made the interpositive using FP4.
> Pyro wasn't involved in that step of the process, so "filtering" wouldn't
> seem to be an issue. I tried putting in another layer of diffusion
> material, which helped, but didn't resolve the problem--and it's very
> inconvenient in any event. I'll check with MIke about his idea about
> "masking." Seems like it would be tough to make it work, but he seems to
> have had success.
> -- Matthew
>
> -----Original Message-----
> From: Carl Weese <cjweese@wtco.net>
> To: alt-photo-process-l@skyway.usask.ca
> <alt-photo-process-l@skyway.usask.ca>
> Date: Sunday, February 21, 1999 8:53 AM
> Subject: Re: negative puzzle
>
> >Chris,
> >
> >This is just a guess but I think you are running into a mismatch between
> >the spectral sensitivity of the specific film you are enlarging on and
> >the color of your cold light tubes. The pyro stain somehow cancels out
> >the problem, so might a "filter" of some sort. If this is a cold light
> >with two sets of different color tubes, turn on the other set as well as
> >the green ones and see what happens.
> >
> >I recently ran into streaks in negatives that only appeared in platinum
> >prints: not when printed in silver, and not visible to the naked eye
> >examining the neg on a lightbox. Apparantly the defects, whether caused
> >in manufacture or in processing, are "visible" only to UV light. The
> >manufacturer is examining them and I don't have a definitive answer
> >about it yet. But you may have a somewhat parallel effect happening.
> >
> >---Carl
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