Enlarger bulb

Discussion in 'The Darkroom' started by Actor, Aug 10, 2009.

  1. Actor

    Actor TPF Noob!

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    It seems to me that one would want to maintain a consistent light level from one's enlarger head. Mine is designed to use an incandescent lamp which immediately suggests two possible sources of error. First, the voltage from the grid is not constant but can vary from a high level during periods of low consumption to low levels during periods of high use. The solution to this would be to buy a dimmer from the local hardware store and set my level to something like 100 volts measured with my VOM.

    Second, and more problematic, is the way in which incandescents die. The filament gives off carbon which coats the inside of the bulb. Cinematographers know that this changes the bulb's color temperature. I assume it also decreases the light intensity. I can think of only one way to deal with this and that is to measure the intensity on a sheet of white paper using a light meter. Given the low light levels used I'm not sure it would work.

    Also, given the way in which variable contrast papers work, I think using florescent bulbs in an enlarger is not a good idea.

    Another possibility is to use LEDs. I'm not sure but given the way in which solid state devices work it's highly probable that their output is consistent until the moment of death.
     
  2. ann

    ann No longer a newbie, moving up!

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    you should use the bulb recommended for the specific enlarger you have.

    what enlarger are you using?

    and, incandescent lamps do shift with time, and with that shift we printers make small adjustments. that comes with time and experience.

    Just start printing and forget the over thinking
     
  3. Actor

    Actor TPF Noob!

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    It's a Bogan. I've had it for almost 40 years. No model number on it. No documentation. The bulb in it is labeled "75 watt, GE, PN/211." The PN is hard to read because the lettering is small.
     
  4. Torus34

    Torus34 No longer a newbie, moving up!

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    Yup. Just start printing. Keep a good record of exposure, negative, paper, filter and enlarger head height and you'll be OK.
     
  5. ann

    ann No longer a newbie, moving up!

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    the pn 211 bulb is a standard enlarging bulb, can be used in a beseler as well
     
  6. Early

    Early TPF Noob!

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    They used to make voltage stabilizers for this purpose, and perhaps they still do. I never had a problem with it in my area as long as I didn't use it on the same circuit as the fridge or other motorized appliance.

    Also, if you are going to replace the bulb, remember that different brands give out different light and color temp. outputs, which would be a problem when printing color. I believe Ann covered that in her explanation. I went from an old Phillips to a new GE and gained nearly a stop in exposure. I also had to adjust my filters to compensate for the colder temp. output.

    Don't throw the old bulb away. I used mine for b&w since the papers were way too fast for me anyway.
     
  7. Actor

    Actor TPF Noob!

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    That's kind of problematic. First, there's no source locally and I can't seem to find it on on-line. Second, if I could find one it would be expensive. The last time I purchased one was over 20 years ago and it cost almost $30 if memory serves. With inflation it would probably cost $50 - 60. Third, there does not seem to be anything special about the bulb other than its price. I doubt there is any spectral differences between it and an ordinary household bulb, though I suspect a household bulb will decay more rapidly, one reason for this thread.

    I don't want to be "OK", I want to be great. I can buy film and processing from Wal-Mart for less than it costs to buy chemistry and paper, and the Wal-Mart product is "OK". To be great you have to pay attention to detail. I guess there's a little bit of Stanley Kubrick in me.

    Least I sound too negative (no pun intended:lol:) I want to thank everyone who has contributed to this thread. Your input is appreciated.
     
  8. ann

    ann No longer a newbie, moving up!

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    the 211 bulb cost about 6-7 dollars, not 50 or 60

    nothing wrong with wanting to be "great, just remember to be good at anything takes time.

    with great printing, it takes a lot of time and practice practice practice. you need to start filling the learning bin with work


    and on by the way, there is a big difference in a household bulb and one made for an enlarger.
     
  9. Actor

    Actor TPF Noob!

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    But what exactly is that difference? Spectrum? Intensity? Longevity?

    There's a big difference between a Ford and a Ferrari but to someone who knows nothing about cars they're pretty much the same until someone comes up with some numbers.
     
  10. CSR Studio

    CSR Studio TPF Noob!

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  11. ann

    ann No longer a newbie, moving up!

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    basically it is how the bulb is coated and where the markings are. on household bulbs it is common to put those numbers in a location that in an enlarger will show up as a defect in your print.
     
  12. Dwig

    Dwig TPF Noob!

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    Quite correct. Enlarger bulbs, the PH series like the PH211, have a heavier white coating referred to as an "opal" coating. This makes is much more uniform. Also, the markings are located around near the base so they don't create a dark spot on the surfaced of the bulb facing the condensors. Substituting a conventional "soft white" lamp will result is somewhat uneven illumination across the negative.
     

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