From: Richard Sullivan FRPS (richsul@earthlink.net)
Date: 09/29/01-11:59:59 AM Z
Sorry I was jumping around and didn't finish editing the message and hit
the send button too soon.
If you pack fluorescent tubes close together it does increase the light
output some but not as much as one would expect.
If you are building a fl bank A good trick is to make a double bank. In
effect what you do is use both sides of the light bank. Build a holder for
your print frame and you can print on top of the bank as well as on the
bottom. You will need to do what I called managed printing. That is the
light bank stays on and you remove the print from the light when it is cooled.
I had a bank like this in California that I did not bring it with me to New
Mexico. (I took out the light unit and never rebuilt it.) It was a work
bench with a glass top and tubes ran underneath the top. There was also a
shelf underneath the tubes. I could print on top or on the shelf
underneath. As you can see, if the tubes are close together all the light
coming from the upper portion of the tubes is lost in a one sided system.
Most people do not concern themselves with printing on this scale but if
you are printing a portfolio for sale as I did in the late 70's (Harry
Smith San Francisco c. 1906) then you are looking for production
capability. I was jumping around like puppy dog in a room full of rubber
balls - coating, printing, washing and drying. You can for production make
up for print speed by having print space in some cases, specifically where
you need to print different negs. If you want to make 25 prints of the same
neg then the difference between a 1 hr exposure and a 10 minute exposure is
significant.
Some points:
Flat bight clean white is more reflective than shiny aluminum or any other
metal including a mirror. Use a base white paint, the one they use to add
color to for room walls.
A fl tube bank is only a point source when the bank is far enough away to
look like a point. In other words at close distances, say for a 2 ft x 4 ft
bank, for anything less than 16 inches, the distance from the bulbs is
insignificant. At 10 inches or 6 inches or 2 inches doesn't matter much.
With a good white reflector behind the tubes you can space them about 1
tube apart and get about a 30% loss of light.
Semi collimated lights with a reflector give more "luminous" prints,
especially with thick emulsion processes like carbon and gum, or POP. This
is due to the image being projected from one direction of light rather than
scattered light.
So if possible forget fluorescents. If you are serious and have the space
go with a industrial metal halide light like Sandy built, it's cheaper,
easier to build, faster in print speed and some would argue gives a better
print.
--Dick Sullivan
At 08:26 AM 9/29/2001 -0500, you wrote:
>Not at all. At least none that I can perceive. I'm using a fluorescent
>tube bank, four inches from the glass, so light is flooding into the glass
>from all directions. Any minute distortions would be averaged out, I would
>think.
>
>A while back, when I was having problems with the lights "coming on",
>someone suggested aluminum foil be placed under the light fixtures, to which
>someone else warned about the problem of errant reflections and hot spots.
>As a crude test, I developed a sheet of paper that I had evenly coated with
>kallitype sensitizer, and used the heavy glass. Exposed for a middle gray,
>I saw no problems with evenness of lighting. I did catch some problems in
>my coating procedure, though...
>
>-----Original Message-----
>From: Judy Seigel [mailto:jseigel@panix.com]
>Sent: Saturday, September 29, 2001 2:13 AM
>To: alt-photo-process-l@sask.usask.ca
>Subject: RE: UV light and Contact Frame
>
>
>
>
>On Fri, 28 Sep 2001, Keith Gerling wrote:
>
> > All of my printing of late has been on 22x30 inch paper. I use a 28x28
>inch
> > piece of "coffee table" glass that is almost a half inch thick, and
>beveled
> > on the edges. Incredibly heavy and awkward, it takes a bit of practiced
> > coordination to move it around, but it seems to do a good job of holding
>the
> > negative flat. I use a piece of carpeting underneath the print. One
>thing
> > is for sure: you won't need to worry about weights or rubber bands. I
> > bought this glass at a place called "Hobby Lobby" that specializes in silk
> > flowers and other weird, kitschy items. They also sell beeswax and
>paraffin
> > at prices far less than other stores.
>
>Keith, I realize this may be just superstition -- but doesn't the very
>thick glass have some kind of distorting effect?
>
>Judy
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