Help with a cold light head

Discussion in 'Enlarging' started by aparat, Nov 6, 2008.

  1. aparat

    aparat Member

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    As I am continuing to learn BW printing I decided to try a cold light head. I had a chance to get an old Aristo head for free, so I thought I'd give it a try. The head came with a power supply. It seems to emit blueish light. I mounted it on my Beseler 23c III and ran a few tests. Overall, I really like the results with Ilford Multigrade RC paper. I used a contrasty negative, without multigrade filters. The tonality was really nice, with lots of highlight and shadow detail.

    However, the light intensity is not consistent. It varies from exposure to exposure. So my question is whether there is anything that can be done about it, or should I just forget about and use my condenser head instead.

    Thanks!
     
  2. Ian Grant

    Ian Grant Subscriber

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    Cold heads need to warm up. I used one for about 30 years with no problems, but for critical work I'd make sure I switched it on for a few seconds, often with a piece of card shielding the paper. Taht seemed o work well.

    Ian
     
  3. aparat

    aparat Member

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    Thanks, Ian. That helps. It makes perfect sense. I will try that when I have a chance.
     
  4. jp80874

    jp80874 Subscriber

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    Read about the Stop Clock Vario, a timer with a light sensor that gives consistent exposure, time after time. http://www.rhdesigns.co.uk/darkroom/html/stopclock_vario.html
    Also if you search here on sponsor R.H. Designs and F stop timer you will find quite a lot of positive feed back. Finding one for free will be a bit more of a challenge.

    John Powers
     
  5. RJS

    RJS Member

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    All my cold lights have had heaters (all are Aristo). There should be 2 cords coming from the light housing. One operates the light, the other the heater. The heater cord gets plugged into a regular switch like a light switch - off and on. On the Beseler enlarger there is a plug on the motor housing to plug into. You leave the heater on while you are printing - the light will feelquite warm. Withouht being warm the tube in the cold light does not go on immediately and tends to flicker a bit. Irregular, inconsitent exposures. With the heater mine is very consistent. Some people feel the need for a feedback sensor arrangement sold by RH Designs with their excellent timer for cold lights, but I have not found the need for one. All my tests indicate good consistency, but by all means look at the RH Designs web page for good information!
     
  6. aparat

    aparat Member

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    Yes! I was wondering what this cord was for. Thanks so much, this is incredibly helpful, as I would have never guessed that the extra cord was for a heater.
     
  7. Rich Ullsmith

    Rich Ullsmith Subscriber

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    No mention of a voltage stabilizer. When the lamp is cold, you cannot achieve much intensity without the source becoming unstable (goes from nice constant beam to a high-freq flickering). A voltage stabilizer also compensates for the light-up and light-down, i.e., voltage is always unstable when turning on and off. I would have to check mine, but the stabilizer is an extra box between timer and enlarger.

    The strong blue hue put off by the light must also be compensated for with VC papers. (Perhaps Arista is different, but still a fluorescent source, thus heavily blue.) This makes no difference with graded papers. A simple color correction filter, light yellow, like a Kodak YCC40 between light and diffuser will bring your unfiltered VC papers to a grade 2 or 2 1/2 (vice about grade 5 without). Of course, once you have the CC filter up top, use regular multigrade filters below for your printing. Hope this was not too convoluted an explanation. Good luck.
     
  8. ic-racer

    ic-racer Member

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  9. aparat

    aparat Member

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    Thanks, that helps a lot! My Aristo head is about 5 inches in diameter. Where can I purchase a Y40 filter of this size? I suppose this could be a simple resin square filter that I could cut to fit the bottom of the cold light housing. Is that correct?
    Thanks!
     
  10. jerry lebens

    jerry lebens Member

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    Interesting Thread : Aristo CC heads are rare (but not completely unknown) in the UK. The CC heads I'm most familiar with are those made for DeVere 54 enlargers. I've seen some of these attached to voltage stabilisers and some not. There's no heating circuit in the DeVere heads and, although I've seen some heads fitted with timers (alwaysmade by Rayco), I always understood this to be bad practice because of the time required to reach a steady output.
    It was more common to have a simple (double pole) switch, in the line between the head and the power supply and to leave the head switched on all the time. Exposure being controlled by swinging a safelight filter into the light path.
    Exposure times tended to be long (30 secs +) and I never heard it mentioned that the output diminished as the head became hotter : Presumably we simply accepted that the head reached a steady state.
    Whether controlled by a simple switch or timer, all switching devices featured 'double pole' switching.
    Regarding the large Y40 flter, You need to find a local supplier for Rosco filters - they make filters for movie making and stage lighting - I usually get them from a shop that sells and hires 'disco' lighting kit, much more common than photo suppliers.
    Regards Jerry
     
  11. Jean Noire

    Jean Noire Member

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    This is my experience too. Just leave the head on whilst in use but check that any stray light is taken of. I use graded papers and have no need of a yellow filter, although this is to be noted for multigrade papers.
    Regards
    John.
     
  12. ic-racer

    ic-racer Member

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    Are you sure about that. There would be over 400 volts going through that switch!

    I don't know about the 4x5 heads, but Aristo warns against leaving the 1212 model 8x10 head on for more than 5 minutes at a time.
     
  13. jerry lebens

    jerry lebens Member

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    Sorry IC, I can't comment on Aristo heads, only the CC heads supplied with the DeVere 54.

    My electrical knowledge isn't great - but I'm pretty certain the switches were double pole, cutting both live and neutral. The DeVere CC heads incorporate a hefty transformer (at least, it looks like a transformer to me) and I understood that, without a DP switch, you were in danger of frying the switch itself. I'm happy to be corrected on this - I'm just relaying received knowledge. It was definitely normal practice to leave a DeVere switched on all day...

    Could it be that the switching was placed in front of the transformer in the DeVere but is between the transformer and lamp in the Aristo? Would this make a difference?

    I'm pursuing this because it occurs to me that the two heads may have practical differences and, consequently, good practice with a DeVere may not be appropriate for operating the Aristo. What's more, might this difference also bring in to doubt the usefulness of an RH timer with a DeVere head?

    Regards
    Jerry
     
  14. ic-racer

    ic-racer Member

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    Ok, I misunderstood your post, I thought you were referring to the Aristo. There are certainly switches rated at that voltage so I guess they could have done it that way or the DeVere may operate with a tube voltage less than the Aristo. I'm not familiar with the DeVere head, but you may be right in that it is a different beast than the Aristo.

    But for the Aristo 1414, the switch is between the mains and the 400v transformer and the switch has 120V going through it.

    Just to elaborate on this a little. One drawback of the Aristo is that there is a current surge when ever it is switched on and off. So, if DeVere is placing the switch between the head and the transformer, this current surge would be minimized.

    Another distinguishing characteristic between the DeVere and the Aristo is that the larger Aristo heads come with this warning from the factory:
     
    Last edited by a moderator: Nov 8, 2008
  15. jnanian

    jnanian Advertiser Advertiser

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    hi

    email or call aristo directly, ask for rick.
    he is a gem of a guy and will help
    you as much as he can. the aristo units
    have a heater, as mentioned, and it needs about 30mins to heat up ..
    you may need to get good at split filter printing :smile:
    or rick may suggest sending the unit to aristo to get
    re-tubed with a v54 lamp ( sounds like you have the w45 ? )
    and you will be good to go with modern vc paper. the w45 works great
    with graded papers ..
     
  16. RJS

    RJS Member

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    If you look carefully on the Aristo site you will find a piece by Howard Bond that appeared originally in the magazine PhotoTechniques. It explainsreally well the difference between theolder W light and the newer V54 and the need or not for yellow filtering and what it will do for you. If you have the older W model you can print ok, so don't worry about it. But do read the Howard Bond piece. And, parenthetically, voltage stabilization is not something for cold lights. Doesn't do anything. To stabilize the utput (if you need to - I don't) you need an arrangement such as RH Designs, the no-longer-made Zone VI or the Metrolux.
     
  17. ZoneIII

    ZoneIII Member

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    You can get a 6x6" 40Y filter from B&H, Calumet, etc. I have one of them that I bought for the reason others here recommended that you get one but I never used it. (I'll explain why below.) Years ago, I switched to V54 tubes which are blue/green and optimized for VC papers. You might want to consider getting one for your head but they aren't cheap.

    For many years, I printed with Aristo heads with the then standard blue tubes. I printed on both graded and VC papers. I had a 40Y filter but I never found its use necessary. When I printed with the blue tubes on VC paper without the yellow filter, I never experienced the high contrast that is often mentioned. In fact, I know several photographers who also found that the yellow filter wasn't necessary when printing with the blue tube and no yellow filter. The only time I would have ever considered using it was when I couldn't get the contrast down enough without it but that never actually happened.

    Now, it's true that it's generally advisable to calibrate your film development to about a #2 grade or a #2 or #2 1/2 filter grade. But if you are small format shooter, there is an advantage to calibrating film development so that a #3 filter is required for a "normal" contrast print. This is because, to do so, you need a softer negative and that means shorter development times and that, in turn, means reduced grain. So if you are shooting small or medium format film, the blue light of your head may be ideal. You actually should calibrate your development with small format film so that it needs higher contrast light to print. I shoot primarily in large format so this isn't an issue for me.

    Let's put it this way. If my V54 tubes went bad today, I would have absolutely no problem printing on VC with my old blue tubes without yellow filters.

    One other point: I would avoid using below-the-lens contrast filters if at all possible. Try to devise a filter drawer that goes above the negative with a diffuser under it. I made one for my old Omega D2 that works beautifully. I have yet to devise one for my 45V-XL but I do almost all of my printing with my venerable D2 anyway.

    I'll try to attach a picture here that may give you some idea for a filter drawer. You can see the one I made in the picture. It has a drawer that holds 6x6" contrast filters and it's bottom is a diffuser. It works beautifully.
     

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    Last edited by a moderator: Nov 18, 2008
  18. selenium96

    selenium96 Member

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    I bought an Aristo head with the older blue tube before the V54 (VC) tube was available. Calumet sold me the 40Y filter with the head and it has been in my enlager ever since. I plug the heater in at least 10 minutes before I start printing and use Ilford MGIV and MG Warmtone almost exclusively. Contrast control with the filters is fine.