Cold Light Variables

Discussion in 'Darkroom Equipment' started by Alden, Feb 16, 2008.

  1. Alden

    Alden Member

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    What do you do about the exposure variables from a cold light? I'll start out with a print taking 8 secs. and by the time I'm to my third or forth print after making burn and dodge adjustments, I'll be up to 13 or more seconds for the initial exposure, which of course begins to throw off my B&D balance? Thanks.
     
  2. Michel Hardy-Vallée

    Michel Hardy-Vallée Membership Council Council

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    Sounds like a case of old tubes needing repairs. How old is your cold light?
     
  3. Dan Henderson

    Dan Henderson Member

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    my cold light does not vary at all from the initial exposure times.
     
  4. jp80874

    jp80874 Subscriber

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    My Aristo 12x12 varies all over the place.

    RH Designs has a probe on their StopClock Vario that measures the amount of light on the first exposure and adjusts the timer so that you get the same or a desired multiple on each exposure thereafter. See http://www.rhdesigns.co.uk/darkroom/html/stopclock_vario.html

    I have had one a couple of years and love it. Search APUG for extensive comment.

    John Powers
     
  5. panastasia

    panastasia Member

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    Cold light sources increase/decrease in brightness as they warm up/cool down, respectively. If you can leave it on most of the time during the printing phase I think you can maintain some sort of stability/consistency - switch it off just before making your exposure. Allow at least 10 minutes on, for warm-up, before making your first print.
     
  6. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Some of the newer heads have heater units that keep the output more stable once they are warmed up. A compensating timer like a Metrolux, though is the best. I've got both on the Arista Hi-D head on my Omega D-II, but my old Graflarger head varies quite a bit. With the Metrolux, I can print stacks of postcards with short exposure times calibrated to the tenth of a second, and they are all consistent from the first to the last.

    Another alternative with heads like my Graflarger that has no heater (eventually I'll get another sensor to use it with the Metrolux) is to keep the light on, let it warm up, and use a shutter or a black card to start and stop the exposure.
     
  7. Alden

    Alden Member

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    Thanks for all the feedbak gents.

    This is a fairly new 5x7 Aristo for VC paper, to replace my still running well, bluish circular Aristo that came with the D2. I bought it to use on a 5x7 Elwood enlarger, but have been using it on the D2 as well for the VC.

    I rarely ever had a hint of trouble with the old one in thirty years of use, and may return it to the D2. Exposure variation did not rear it's head with this old boy much at all. Are the new one's still made in the states, I wonder?

    The contrast problem was also something I finally read about, but had not noticed either. My negs are perfectly normal in contrast and I still used no.1 or 1/2 filters all the time with old blue, and still acheived excellent blacks.

    I'll try and learn the new one's characteristics, as I don't have a large output that requires a lot of multiples, to warrent a compensating timer. But thank you again for the information. Maybe a used timer, would be nice.

    Ken