----------
From:
alt-photo-process@cse.unsw.edu.au[SMTP:alt-photo-process@cse.unsw.edu.au]
on behalf of tomf2468@pipeline.com[SMTP:tomf2468@pipeline.com]
Sent: Monday, July 15, 1996 12:01 PM
To: Multiple recipients of list
Subject: Re: UV output
Hello Glenn, I wondered about this also when building my UV box. Some
simple "visible light" metering, and some experience with "cold lights"
for
silver work convinced me that the first 45 seconds or so were "uneven"
(always less light than further into the exposure).
But,,,,, some simple math showed this not to be of much concern. Even if
the first 45 seconds averaged 50% low in output (MUCH more error than I
got), then "in my case" an average exposure of 12:00 would get 96.8
percent
of it's "correct" light (11:15 plus 50 percent of 0:45 equals 11:37).
96.8 percent is equal to a 1/21 (0.048) of a stop error! Don't know about
you, but I can't be that consistent using eye droppers when I mix my
chemicals!?!?
Also, just a few minutes in between exposures cools my tubes off again (I
have a fan in my unit, seemed to help with gum printing), and the process
was thus "repeatable". So..... my advise is to worry about the many
things
that do impact your work, and happily ignore this one.
tomf2468@usa.pipeline.com (Tom Ferguson)
On Mon, Jul 15, 1996 9:00:43 AM, glennon@netcom22.netcom.com wrote:
>My business partner and I have built a UV lightbox, using commercial
>grade, uncoated blacklight florescent tubes. It works great, but
>we've been having a "discussion" about the output of the tubes. He
>feels that the tubes have a "warm-up" time and ought to be on for at
>least 5 minutes before use. I put the box on a darkroom timer, so
>that it turns on at the start and off as the time ends. <SNIP>
>Thanks all.
>
>Glenn Cannon
>glennon@netcom.com
>http://www.newart.com/cannon
>
>Platinum Portraiture Studios
>Huntington Beach, California, USA