Re: WATTS - Hot light, Cold Light


"John J" <nohj@xxxxxxxxxxxx> wrote in message
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Richard Knoppow wrote:
"John J" <nohj@xxxxxxxxxxxx> wrote in message
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Briefly: For strictly black & white printing, does a
cold head gives as much _usable_ light as, say, four
150W tungsten bulbs? Four 250W bulbs? Do the cold lights
give more effective light per-watt?

You see, I was given that might (might) be suitable for
a light head for the Saltzman 8x10" enlarger. Maybe. It
is steel, uses four Edison base bulbs with wiring
sufficient to accommodate four 250W bulbs. It has four
150 bulbs now. (GE brand with the printing on the side
of the bulbs.) The bulbs are on the sides of the box, in
reflectors and shielded from direct view of the negative
carrier. And there are two fans in it and it's light
proof vented, and it has a large, thick, heatproof glass
over the open part. I do not think it was ever an
enlarging head. For good reason, I'll bet.

(If it is important I can make a snapshot to post to my
web site.)

Thank you, all.
--
JJS in MinneSnowta

I'm not sure what you have but it might have been an
illuminator of some sort. There were lamphouses along
those lines used on enlargers.
In general flourescent lamps, including the compact
type, produce quite a bit more light per watt than
incandescent lamps. I don't think there is a definite
ratio but I would say about four times the light. For use
on an enlarger using variable contrast paper the phosphor
color needs to be selected so that the filters will work.
Normal "cold light" enlarger lamps were pretty blue and
require a yellow filter to get any sort of range and then
its compressed. I think the warm-white compact lamps that
look like tungsten may work pretty well but you will have
to try them and the filters will probably not have quite
the same contrast or spacing that they do with a tungsten
lamp. The compact flourescents will dissipate a fraction
of the heat of a tungsten lamp with similar light output.
You can get compact lamps with light output equal to at
least a 200 watt tungsten lamp at many stores but I don't
know if they come in all colors.
For graded paper the blue lamps work fine.

Thanks, Richard. I think you are talking about the bulbs
available to replace ordinary tungsten Edison based bulbs.
If that's the case, then I will go to the home supply
place today and get a couple and first try them in the
Focomat Ia! What better way to test without spending a
lot? If the bulbs are not suitable, I'll put them in the
workshop. :)

Rise-time concerns me, but I'll find out!

JJS

One problem with any gaseous discharge lamp, which
includes all fluorescent lamps, is that the output varies
with temperature. The lamps like to run hot and in an
enlarger should preferably be run continuously. The original
lamp house used in the Saltzman employed mercury vapor
tubular lamps which were run continuously so that exposure
was controlled by a shutter similar to the Packard shutter
which was held in front of the lens on a fixture. A shutter
also give precise control of exposure, large tungsten lamps
have a lag on turning on and take a short time to fade out.
Not a problem for the small wattage lamps found in most
enlargers. The compact fluorescent lamps are cheap enough to
allow testing plus if they don't work you can use them
around the house.


--
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx


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