Aristo cold light question..

[Robbie Bedell]

I recently bought an Aristo cold light for my D2 enlarger. I have had one once before, a Zone lV. I bought this head for a project which requires printing old negatives which have been attacked by mold. This bulb is the older v45 so I have the yellow filter in it and that part works just fine. My problem is that I am getting inconsistant exposures. After I make a test strip of say, 10 sec. and determine I need a nine sec. exposure, I make my print at the nine sec. I then make a second print at the same 9 sec. and it is sometimes darker and sometimes lighter, by at least one whole stop. I know there is a heater in the head to keep the bulb warm. The heater cord is plugged in. Is it possible that the heater is not working? After it has been on for some time I touch it and can feel no heat whatsoever. Perhaps I have a voltage variation problem. Can anyone suggest a simple voltage regulator, if that might be the problem. This is frustrating because I do like the results I am getting when things do work out. I am not new to printing. I have been printing on my two D2s and focomat for many years and worked for newspapers for more than 20 years and never had such a variation in times without being about to troubleshoot the problem. Can anyone help!

http://robbiebedell.photoshelter.com

[Kodachrome25]

Hi Robbie, you will relieve your self of the headaches of a Aristo Cold Light Head if you use a compensating timer with the sensor which reads the true output of the lamp in real time and then feeds that info directly to the timer.

There are a couple options, one hard to find, one easy. The hard to find one is a Metrolux-II compensating timer with probe which is no longer made and pops up on eBay only on occasion. Then there is what I now have and that is a RH Designs StopClock Vario with probe and is truly excellent. The Vario uses the popular "F-Stop" method of exposing paper, a bit of a learning curve but after no time at all, it all makes sense. Richard is great to deal with and his products are superb, in addition to the Vario, I own the paper flasher and process timer.

The Vario is by no means cheap, but it works out to saving money in paper and frustration in the long run. That is what I did and there is no going back, it just works...

Worse case, you buy and use the Vario just for the project, then if you feel like it, sell the timer and the head as an enticing package and will most likely still come out ahead in paper and time savings...

Good luck either way you go!

[Jon Shiu]

One possible thing to try is to leave the bulb on so that is warm. Turn it on 10-15 minutes before printing. Have to work out a way to block the light with a lens cap or red filter when loading the paper into the easel. Can use a hand held card to block the ligtht when removing the cap or filter to start/end the exposure.
Jon

[Doremus Scudder]

One possible thing to try is to leave the bulb on so that is warm. Turn it on 10-15 minutes before printing. Have to work out a way to block the light with a lens cap or red filter when loading the paper into the easel. Can use a hand held card to block the ligtht when removing the cap or filter to start/end the exposure.
Jon

Ditto! I used this method successfully for years. The only downside is a bit shorter bulb lifespan. I print using a metronome, so it was easy to just cap the lens, put the paper in the easel, hold a card under the lens, start the metronome, remove the cap and then pull the card to start the exposure.

If you use a regular timer, you can do the same, just set the timer for a few seconds more than you need and pull the card at the appropriate moment.

If you have an enlarger that leaks light (as most do), you may want to rig some baffles to keep stray light from bouncing all over the darkroom. I just cut up some of the lightproof paper bags and hung them with tape from strategic point on the enlarger.

Do turn on the head 15 minutes or so before making your first exposure, as Jon advises.

Best,

Doremus

[Brian Ellis]

You might be able to find an enlarging meter like the one Ilford makes or used to make. Mine cost about $25 new. I found that I didn't need it with my Aristo VCL4500 head so I seldom used it and don't remember the details. But IIRC it was pretty simple to use.

I owned the Metrolux II timer someone mentioned. Mine cost about $250 new about 15 years ago. I don't know what used ones sell for today if you can even find one. However, IMHO they're overkill for your problem, which sounds mostly like a stabilization problem. I bought mine mainly with the hope that it would allow me to go from a small print to a larger one without having to re-test or re-check the exposure, dodge, burn, etc. times. It worked less than perfectly for that purpose.

[Robbie Bedell]

Thanks so much for all of your information! It appears that the best solution would be to find a compensating timer someplace. But what I don't understand about this unit as it is, why if it has a built in heater which I plug in a half hour before printing, why it doesn't keep the bulb warm already without having to keep the bulb on? What is also strange is that sometimes the exposures are fine. I did a test yesterday and made three prints of the same neg and they were all fine. Then the next neagtive the times were not consistant. I may just go back to the Ilford 400 that I used earlier..Thanks you all again for your wisdom!! Robbie

http://robbiebedell.photoshelter.com

[Joseph Dickerson]

Robbie,

You don't say what timer you're using but the power requirements of the Aristo heads is too great for many enlarging timers. It actually fries the contacts. Hence, the timer will very quickly become unreliable, this might be what you're experiencing. A relay between the timer and the head will solve the problem, as will using a proper timer. Aristo used to have a list of which ones would work, I believe that the mechanical Time-O-Lites were fine. Many electronic timers simply couldn't handle the load.

If the head is not warm to the touch, not hot mind, just warm, the heater is not working and could also cause the problem you are experiencing as the tube will increase it's output as it warms.

Leaving the lamp on and using a card to block the light as Jon suggests, and an inexpensive metronome for timing will allow you to check if the problem is your timer or a heater issue. To me it sounds like it's a combination of both.

JD

[ic-racer]

Is it possible that the heater is not working? After it has been on for some time I touch it and can feel no heat whatsoever.

I'd say that is the definition of 'not working'

Check the thermostat and the heater elements for continuity. In my Aristo, the heater elements are just power resistors shorted across the mains.

[ic-racer]

When the heater is working correctly, you should be able to get excellent repeatable results by allowing the temp to stabilize between prints.

[SpeedGraphicMan]

Sounds to me like the heater is DOA.

You can repair it... Or just leave the unit on while using it...

A lens cap for your enlarger comes in handy in this instance.