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  1. #1
    Dave Wooten's Avatar
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    Making a Cold Light

    Specific color temp. recommended if one was to construct a large cold light head...any off the shelf bulb suggestions? straight tube bent tube curled tube etc....?

    thanks again all!

  2. #2
    David A. Goldfarb's Avatar
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    14x17" isn't big enough? I've seen things made from straight tubes, if that's what you're thinking, though I think the ones from Aristo are made with long custom curved tubes.

    Well, whatever you decide on, you might look and see how the heater circuit works in the newer cold light heads. One downside of cold light is that the bulbs have a ramp up time that makes it difficult to get consistent output without something like a compensating timer (Metrolux) that reads the output and adjusts the time accordingly. The current style Aristo heads have a heater in them that keep the bulbs warmed up between exposures for much more consistent results without a Metrolux.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
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  3. #3
    Dave Wooten's Avatar
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    thanks,

    confession, some of my street project stuff is done on "small format 5 x 7" and the 7 x 17.5 cameras I am testing...these will be enlarged to minimum 16 x 20 etc.....so I have recently "raided" e bay and added to my omega enlarger stash. D 2, D 2V, E5 omegalite-(bulb burned out need to find replacement...hopefully off the shelf) E5 condensor, B8 condenser, 2 B3 and 2 B22...also a "retro elwood 5 x 7--love that shape-being repainted possibly in psycho colors....and a lovely bessler 45 left out in the street for the taking.thus the question for off the shelf bulbs and also to construct a larger enlarger am looking at using the columns from an omega or bessler 45m to hold a lite for 2 x enlargement of the 7 x 17.....possibly this will have to be on a horizontal track but dont think so at 2 x etc....

    the enlargers are intended for near future use in planned analog teaching lab.

    Can you believe a perfect E5 enlarger with lenses, table and neg carriers for 66 bucks.....I just love this digital fad.

  4. #4
    Mike-D's Avatar
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    I've used a "deluxe warm white" which is nearly 3200k with a high CRI. CRI or color rendering index sort of measures how close the lamp comes to continuous spectrum. Cheaper lamps have spikes at certain color frequencies.

    Not sure how much that matters, but that lamp worked well with VC filters.

    Mike D

  5. #5
    L Gebhardt's Avatar
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    Why not try making a VC head out of LEDs? They are very bright and use little power. An array of blue and green LEDs would make a good VC head. I have seen some plans on the net in the past and they looked simple enough to make. I am thinking of making a 5x7 head this way.

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    jimgalli's Avatar
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    Dave, As above, some of the stuff they're doing with LED's is fascinating but I'm completely ignorant. Hey, how many $15 Costco flashlights could it take? Wonder how the LED's would do as UV for the Pl / Pt's?
    He is no fool who gives what he cannot keep..to gain that which he cannot lose. Jim Elliot, 1949

    http://tonopahpictures.0catch.com

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    Mark Fisher's Avatar
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    FYI - you can get ultra bright LEDs from places like digikey.com for about $2.50 each in blue and green. If you can adjust the voltage to the LEDs, then you have a VC head. There is someone who hooked up an LED head to a RH analyzer: www.huws.org.uk It is on my list of things to do (I have a long list!)

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    Quote Originally Posted by jimgalli
    Dave, As above, some of the stuff they're doing with LED's is fascinating but I'm completely ignorant. Hey, how many $15 Costco flashlights could it take? Wonder how the LED's would do as UV for the Pl / Pt's?

    I have used 395 nm UV LEDs in an attempt to expose Azo. My attempt was unsuccessful even when the LEDs were immediately adjacent to each other. Pt-pd would be even more problematic.

    The UV LEDs do not emit enough light even though the emission is in the appropriate band.

  9. #9

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    Quote Originally Posted by Mark Fisher
    FYI - you can get ultra bright LEDs from places like digikey.com for about $2.50 each in blue and green. If you can adjust the voltage to the LEDs, then you have a VC head. There is someone who hooked up an LED head to a RH analyzer: www.huws.org.uk It is on my list of things to do (I have a long list!)
    It's not a matter of adjusting voltage, since the LEDs require a specific voltage to operate, but rather having a circuit to switch them in and out of the circuit.

  10. #10

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    Quote Originally Posted by Dave Wooten
    Specific color temp. recommended if one was to construct a large cold light head...any off the shelf bulb suggestions? straight tube bent tube curled tube etc....?

    thanks again all!
    A lot depends on what you are wanting to print on. If you were printing on graded material a F15t8BLB would give you very short printing times. It may also work on Azo...the problem is that this is a black light bulb with high UVA output.

    For VC and graded materials using VC filters I would lean towards a F15T8DSGN50 which has a color temp of 5000 Kelvin.

    Both of these bulbs are off the shelf items at Bulbman. They should be able to fix you up with the correct ballasts for these too. These lamps are about 18 inches long and you could lay them side by side and six should give you the width that you need for your 7 inch negative width.

    I would plan on six lamps and three ballasts.

    The other thing is what someone already mentioned. That is that these lamps will drift as they warm up. The answer is to use a light integrator or a Metrolux timer. The other thing that could be done is to incorporate a shutter into the enlarger design. A Packard should work if you pull the pneumatic actuator and replace it with a low voltage (24VAC) electrical solonoid (available at WW Grainger and Johnstone Supply). Doing that you could leave the lamps on continually while printing and have your timer switch the solonoid and the shutter. A switching relay circuit would need to be built...but that is not rocket science.

    If you decide to go the shutter route it would require a 24 VAC solonoid, 115V-24VAC 100 VA transformer, a double pole single throw relay with 115VAC coil voltage, an enclosure, SJ 14/3 cord and grounded plug.

    Good luck...sounds like fun.

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