I'm interested on purchasing a VC cold light for my Beseler 45 VXL and I've the following questions :

1)I'v heard about a "warm up time" (vs instant light of normal lamp) when you turn on the cold light head before printing ? Is it true or not ? If it is true, how do you manage this warm up time?

2)Did somebody already used the 45 VXL with a VC cold light head and what is his opinion ?

Thank you for your answers

Jean-Bernard French Photographer from Toulouse (France)

-- Jean-Bernard Roux (jeanbernard.roux@voila.fr), September 23, 2001

Answers

Response to Using cold ligh head

I use on an old Beseler MX5 enlarger a Zone VI variable contrast light head with 2 tubes, one for high contrast and the other for low contrast. It comes with a controller for varying the relative amounts of the two different light sources. I'm not sure if it's a current model. I used to use an older Zone VI single tube head for graded papers.

Yes, it is true that there is a big shift in light intensity which apparently is a function of the tube temperature. With the old single tube head, there was a light sensor in the head, and this was used with a Zone VI light stabilizer, which in effect set the light to a level that it could maintain. This had the disadvantage that the light was always quite a lot less than max, but it was very constant.

The newer two tube device runs at max if you want, but the timer is set in "units" of light rather than seconds. The timer makes a "tick" sound for each unit during the exposure. The "tick" length shortens as the lamp(s) heat up. It works well. You can really hear the acceleration of the ticks as the tube heats up.

I think it would be impossible to use cold light heads for fine printing without some procedure to take this variation into account. Maybe if you left the tube on all the time and controlled it with a shutter?

-- John Stockdale (jo.sto@bigpond.com), September 23, 2001.

Response to Using cold ligh head

Just to clarify what what John has said, there are 2 types of cold light head suitable for VC printing.

One is the very sophisticated head discribed by John which has 2 tubes, one for low contrast and one for high contrast. The controller mixes the light in the tubes to achieve the desired contrast. The one made by Zone VI (sold by Calumet) has the built in tempature controller that various the time automatically. Aristo also makes a similar product, but I don't know if it compesates for tempature variation. Both of these cost over $1,000 USD.

Aristo also makes a "regular" cold light head using a single "V54" tube that is compatiable with VC filters (although there is no filter drawer provided with the head). These heads do not contain built-in time compsentation like the Zone VI model, but they do have a tube warmer that should be plugged into the electrical outlet at least 10 minutes before printing. The tube warmer helps, but does not completely solve the problem of light intensity drift. These models cost about $250 USD new. To completely compensate for light intensity drift, it is possible to purchase a Zone VI compensating enlarger timer (which also requires that a light sensor be added to the existing cold light head). Both the Zone VI compensating enlarger timer and light sensor can be purchased from Calumet for about $500 USD. Sometimes these are available used on e-bay.

Another solution is a used Zone VI Cold Light Stabilizer (no longer made) that is sometimes available on e-bay (also requires the installation of the light sensor on the cold light head). The Zone VI Cold Light Stabilizer requires the use of an external timer. One recently sold on e-bay for a bargin price of $75 (See copmpleted ebay item 1274649014) but they usually go for about $200.

There are many older Zone VI and Aristo heads without the V54 tube that do not work well with VC filter sets. These can be purchased used on e-bay for about $75-$125 USD. It is possible to upgrade some of these to V54 tubes for about $115 USD. They also work with the Zone VI Compensating Timer or Cold Light Stabilizer.

-- Michael Feldman (mfeldman@qwest.net), September 23, 2001.

Response to Using cold ligh head

Correction to my post above. In paragraph 2, instead of "tempature controller" or "tempauture variation", I should have said "light duration controller". As John has explained, the Zone VI model actually does not alter the intensity, but it varies the exposure time to compensate for the light variation of the tubes. The problem is related to tempature variations of the tubes, but is rectified by measuring the light output and altering the exposure time.

The Zone VI Cold Light Stabilizer (which I use) measures the light output of the tube and various the voltage applied to the lamp to maintain a steady light output.

-- Michael Feldman (mfeldman@qwest.net), September 23, 2001.

Response to Using cold ligh head

I use the Aristo VCL 4500 on my Beseler 45MX. The unit has a built in heater that helps to stabilize the output. Before I prepare to print I turn the unit on, not the lamps, and let the heater warm up for for at least 15 minutes. After that, I print as normal. I have never experienced light output fluctuations from print to print. I am very pleased with the system and only wish I had converted to it years ago.

-- Jim (jimzpace@yahoo.com), September 24, 2001.

Response to Using cold ligh head

Yes, there is a warm-up time before you can use full light output, but it is not very consequential. Just turn the enlarger on when you start setting up the darkroom for your printing session, and by the time you are ready, the enlarger will be, too.

This is a "power on" warm-up, not a warm-up for each exposure.

Best regards, Charlie

-- Charlie Strack (charlie_strack@sti.com), September 24, 2001.

Response to Using cold ligh head

I use an Aristo VCL 4500 on my Beseler 45V XL. With it I use the Zone VI compensating timer, which corrects exposure times when the cold light head is not fully stabilized. It's a very effective combination.

-- Ted Kaufman (writercrmp@aol.com), September 24, 2001.

Response to Using cold ligh head

Ted, Did you install a Zone VI photocell (that connects with the Zone VI timer) into your Aristo head? If there is only one photocell and two tubes, where did you place the photocell?

-- Michael Feldman (mfeldman@qwest.net), September 24, 2001.

Response to Using cold ligh head

Michael: Yes, I did install the Zone VI photocell. I drilled a hole in the top of the cold light head to mount the photocell.

-- Ted Kaufman (writercrmp@aol.com), September 25, 2001.