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xkaes
30-Jun-2017, 08:12
Another, unrelated, post caught my attention because I have a Beseler P-III Cold Light Head that I have never used.

First, I have never used it because cold light is "different" is certain ways, such as light color on VC papers, etc. and I have enough things to deal with. Second, I'm happy with my current light options, both for B&W and color. I have a Beseler CB7 and a 45 MXII. A point light source for both, standard condensers for both, both diffusion & condenser (yes, Beseler offered this option) color heads for the MXII. So I can vary the contrast as much as I need. I'm satisfied with my results, but maybe I should try out my P-III, and then decide to use it, or sell it. All it does now is gather dust.

However, I don't now how to use a cold light head (I have lots of material on that if I want to go down that road), and I can't find anything about the P-III. But I know it works. Beseler made a "Model 45" cold light head which kinda, sorta, looks like the PIII, but I assume it won't fit on the CB7. And I might be able to adapt the P-III to the 45MX -- should I REALLY lose my mind! Here is the P-III:

166651

It looks kinda, sorta, like an Aristo/ZoneVI cold light head, but not quite. It is too large/wide for the MXII. It came with my CB7 -- and fits it fine -- but my CB7 manual only lists the condenser and color heads. I can't find anything on the web except for the Model 45. Like other cold heads, it has two electrical plugs. There is no ON/OFF switch. One line turns the bulb on -- which I assume should go to a voltage stabilizer (I have one of those), and then to a timer. The other, I assume is for a warmer, pre-heater(?) and left on all the time?

Any details, hints, help, or suggestions would be appreciated. It's not anything I am going to tackle today. Like I said, I've got lots of books about using cold light if I want to actually use it. Is the a fork in the road I should avoid?

Doremus Scudder
30-Jun-2017, 10:00
Cold-light heads are very much the same. If yours is anything like the ones I have and have worked with, you should have two power cords, one for the heater and one for the lamp itself. The heater cord should be plugged in some time before you actually start printing (15 min or so) so the unit can come to temperature (cold lights are really warm...). This keeps the light itself from varying too much in intensity. The lamp then gets plugged into a timer and controlled as usual from there.

See page 18 and 19 about the "Beslite" here: http://www.jollinger.com/photo/cam-coll/manuals/enlargers/beseler/Beseler_45M.pdf

Zone VI made cold lights and cold light stabilizers that incorporated an optical sensor and a feedback loop to keep the lamp at even output. Even with the heater, they can tend to drift a little. I used to just leave mine on for the entire printing session and start exposures by removing the lens cap. This, of course, used up the lamp faster, but I had a replacement. Nowadays, with replacements harder to find, that may not be such a good idea.

Hope this helps,

Doremus

xkaes
30-Jun-2017, 10:24
Thanks for the info. I figured that the bulb is basically impossible to replace. Fortunately, fluorescents last quite a while. I haven't taken it apart to see what # bulb is in it.

Judging from the articles I used to see if photography magazines in the 80's, I thought cold light was pretty popular back then. Has it grown in popularity or has the luster been lost?

fuegocito
30-Jun-2017, 10:49
I think this is one generation after the original Beseler cold light head, which has only one power cord that lights up the head. The cold light bulbs are available but particular fit/modle may or may not be available. I have to do some digging but it's a company in Connecticut, I bought a replacement bulb from them for a Graflex enlarger cold light head.

dsphotog
30-Jun-2017, 12:02
Don't forget to unplug the heater cord, when done printing.

Eric Woodbury
30-Jun-2017, 13:59
X, voltage stabilizer will do you no good. Lamp output variation is the related to the temperature of the gas in the tube and the phosphor, but not the voltage. If the temperature is maintained properly (but it seldom is), then light output is constant. With light on and off and heater on, there are still variations in temp. As noted above, some just use the lens cap as a shutter and leave the lamp on. This can work, too. Otherwise, a closed loop timer/controller is required.

Cold lights last about 10,000 hours of on time. They are still popular, but as the bugs of LED light source are worked and prices come down, they will fade. Coldlights are very bright sources for fast printing of large format. That's good. Tubes are fragile and are easily broken by FedX or UPS. That's bad. Good luck. EW

xkaes
1-Jul-2017, 06:12
Thanks for the tip on the voltage stabilizer. I'm leaning toward giving it a try, but I don't really see it as being much different than a standard diffusion head. I haven't done any EV light comparisons, but are cold light heads significantly brighter than standard diffusion heads?

It all makes me wonder if there was a P-I, P-II, P-IV, etc.

Luis-F-S
1-Jul-2017, 06:33
Judging from the articles I used to see if photography magazines in the 80's, I thought cold light was pretty popular back then. Has it grown in popularity or has the luster been lost?

Cold light heads IMHO were popular because dichroic heads were so pricey back when. If it's one of the older W-45 bulbs, you need to ad a 40CCY filter to use with VC papers. If you can't find the 40CCY, then use a 30CCY! If you have one of the newer W-54 bulbs (not likely) then you're good to go. Cold light head sources work best when used with some sort of a compensating timer that measures the light output. This requires that a photocell be installed; the Zone VI light sources came with one. My favorite is the Metrolux timers which vary the "length" of the time to adjust for changes in the light intensity. Once you use a cold light head, you'll not go back to a condenser light source. I printed with cold light sources for years until I got an enlarger with a dichroic head, or an LPL with a VCCE head. If you have a dichroic light head on your 45MX you're not likely to use it unless you want to use it with your larger enlarger. I was not aware that anyone made a cold light head for the CB7 Beseler enlarger. If you're not going to use it, you might want to list it to see if anyone has interest in it that could actually use it. L

xkaes
1-Jul-2017, 07:08
I've got the Beseler dichroic 45 S diffusion head which uses EVW 250-watt 82-volt quartz bulbs. I don't know if those would be W-45 or W-54 bulbs. For B&W enlargements, when I use the diffusion head, I set it to white light and use Ilford VC filters. For more contrast, I can use the condenser head -- or for PUNCH, the point light source!

Luis-F-S
1-Jul-2017, 07:17
Those are dichroic bulbs ; has nothing to do with the W-54 fluorescent bulbs