From: John Campbell (tojohn@texas.net)
Date: 03/28/02-03:18:22 AM Z
Rip Van Winkle lives!
--but he has yet to catch up on follow-up posts.
Parallel may be best, but series is better!
(I'm just glad this isn't about S&G!)
Oy, vey.
G'night all,
--John
http://www.photogecko.com/
Home of The Gecko UV Light Box
"Get The Gecko!"
-----Original Message-----
From: William Marsh [mailto:redcloud54@earthlink.net]
Sent: Thursday, March 28, 2002 3:33 AM
To: alt-photo-process-l@skyway.usask.ca
Subject: Re: Light source for big prints
Judy, did you wire the ballast in parallel or in series? Makes a big
difference in the way voltage is distributed to each fixture (parallel
is correct).
Bill
Judy Seigel wrote:
> Judging by my own tests (shown Post-Factory #7), any of these
> configurations should be fine. Probably. But I found an easy "low tech"
> way to test & advise something of the sort for every system because there
> may be pitfalls.
>
> Dilute cyanotype emulsion 1 to 2 with water, coat on some cheapo paper the
> size of your light bank and expose for the minimum exposure to get tone
> (pale shows uneven better than dark). In my case that was 30 seconds.
>
> Don't try to do it with 21-steps, in which the readings are too close &
> with too many variables, and the difference between wedges can throw
> things off. You can't do every inch anyway. Coat the whole paper & read by
> overall glance.
>
> Even with every other bulb covered, it still came out even, even at only
> 1-1/2 inches from the bulbs.
>
> *BUT*, surprise! Top to bottom of the light table there was a difference,
> that is, about the bottom 4 bulbs gave noticeably less density than the
> top. I tried coating from different directions, I put a white reflector at
> the open end.... Could the electricity be wearing out on the way down?
> Finally I switched the top 4 bulbs with the bottom 4 bulbs & all was even.
>
> No I can't explain it.... but I show it ... scanned the whole sheet &
> copied a wedge from the bottom in Photoshop & pasted into the top.
> Difference is very distinct. I'd suggest a test of this type for EVERY
> light table, but ESPECIALLY if you didn't get all bulbs at same time from
> same lot. Interestingly (baffingly), even when several bulbs in a row were
> out (by accident), the difference was less marked.
>
> Judy
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