Re: Light source for big prints

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From: William Marsh (redcloud54@earthlink.net)
Date: 03/28/02-04:17:16 AM Z


Sorry John. I've been out of town for awhile. and as it's 4 AM, I may
not be fully functional.

I thought it was always better to wire in parallel because of the old
experiment with light bulbs wired in series, that produces a drop off in
light output as you go down the line.

Forgive my blanket pronouncement from before.

Bill

John Campbell wrote:
>
> 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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