Non scientific CFL/enlarger experiment.

Discussion in 'Darkroom Equipment' started by JBrunner, Dec 26, 2007.

  1. JBrunner

    JBrunner Moderator Staff Member Moderator

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    I decided to run a bit of an experiment. Now, the CFL thread is moldering in the Soapbox, so if you want to rant about CFL's, and the incandescent ban, go there.

    This is just about trying to get one to work in an enlarger.

    My Besseler 5x7 diffusion enlarger takes edison type bulbs, so I decided to try out a a biggish spiral CFL in it, as I don't have a regular bulb for it yet.

    The results of my hillbilly experiment are as follows:

    As long as the lamp was warm, on/off cycles were predictable and consistent. If it cooled for more than a minute or so, I had to run it back up to temp to get it consistent again. A huge PIA, but sort of functional (kind of.. maybe).

    The first image shows the projection with out the diffuser, focus set to the lamp. Now, nobody would expect this to be pretty, but it reveals an unexpected problem, at least with this particular lamp housing. You can see the lamp and housing, as expected, but the interesting part is that the spirals of the bulb, probably because of self masking in the spiral, and reflection/refraction angle, separate the green spike of the discontinuous spectral output, creating a neato (unless your trying to print with it) green hurricane looking thing. This is what the diffuser "sees" before it goes to work.

    The second image is with the diffuser in place, but still focused on the lamp house, the green hurricane is diffused, but still readily visible. The fall off is a result of having the focus up in the lamp house.

    With the focus set for projecting a negative to about 8x10, the light evens out (of course), and the camera couldn't pick it up, but I can still see green mottling with my eyes. With an incandesant, the smooth surface of the bulb is of course going to be more even, but with the spiral CFL, differing amounts of green here and there on the diffuser is death to contrast control on VC.

    Conclusion- as of now, no go diggy di. I'll try some mods, if I think of any. My first idea would be to go get one with the plasic bulb looking envelope around it, but they are of much lower output. It is possible that the output spectrum will make up for that, except I'll go blind trying to grain focus.... More to follow.
     

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    Last edited by a moderator: Dec 26, 2007
  2. Removed Account

    Removed Account Member

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    This gives me an idea for a test; at work I saw we have some red CFLs from Phillips and I still have a pack of 5x7 RC paper around here. I'll see what happens safe-light wise...
     
  3. Mick Fagan

    Mick Fagan Subscriber

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    The first thing I thought of when I saw the first picture was the advertising line, "Guess who's mum, has a Whirlpool?".

    Pretty neat experiment.

    There was an article recently in the financial part of my newspaper, about a fellow who has invented cold light, lights, to replace the hot down lights that seem to be in every second house.

    Basically he has taken the non heat emitting parts of the light spectrum and managed to produce some quite amazing lighting effects.

    It appears that this may be the answer to some of our energy problems in the future as their efficiency is quite amazing and effectively, they don't emit heat. In fact they are apparently so efficient that you can actually hold the light globe in your hand, whilst it is illuminated.

    Mick.
     
  4. jnanian

    jnanian Advertiser Advertiser

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    jason

    some of the early omega e3 enlargers had regular fluro tubes in them .. not the round omega lite that looked
    like an alien bug, but the square box ... the way they got over the heat up/ cool down of the light source
    was to have a shutter near the lens stage or below the lens ( never seen one so i don't know for sure ) ...
    if you have a spare shutter, who knows it might help with your experiments :smile:

    good luck!

    john

    ps. cool vortex!
     
  5. Curt

    Curt Subscriber

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    I bought the 11x14 Kodak Opal glass that was on the eBay for a month, I'm going to experiment with different light sources, CFL, LED, diffusion box, incandescent, etc.. Something will fit the bill, I do have an 11x14 Aristo head but it has the old bulb and is one color temp.. I wonder if I can adapt an old Beseler color head into an 11x14 light source by changing the bulb and using the filters. Strip it out and use the parts in a diffusion chamber. Styro material lined.
     
  6. Jon King

    Jon King Member

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    I was inspired by the same thread, but I started with some step wedges and a $25 desitometer from ebay before printing - the printing is next.

    I replaced a 160 opal bulb in a Durst 138 with a 42W CFL - The contrast curves using split grade filters (very yellow, very magenta), are the same, except there is a stop and a half increase in speed with magenta. I didn't see any spiral pattern, but that may be due to the enlarger design - when making real prints, I'll see what is really there.

    I have curves and all that to post, but I don't want to hijack Jason's thread - besides, the proof is in the print :smile:
     
  7. JBrunner

    JBrunner Moderator Staff Member Moderator

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    John, feel free to post your information here. I think it is completely relevant.
     
  8. Murray@uptowngallery

    Murray@uptowngallery Member

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    Thanks for trying this and sharing.

    I have been trying to get a friend to do this for me with a green spiral CFL in his small enlarger that has a diffuser to see if it's possible to get usable contrast range on VC paper with green light only. Ilford's paper shows a long gradual slope on the HD curve but a lower contrast range.

    He has the lamp, and hopefully over the holidays he'll give it a try.
     
  9. Jon King

    Jon King Member

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    Another CFL experiment

    Short Version:

    Replacing a 160W incandescent bulb with a 42W spiral CFL should work for split grade printing, yielding similar contrast and printing times or low contrast (yellow filter) exposures and a speed increase of 1.5 stops with a high contrast (magenta filter) exposure. Unfiltered contrast was significantly different.

    Longer Version:


    I used a Durst L138 enlarger, 100mm lens, enlarging a 120 step wedge approximately 4x. The step wedge was a 21 step wedge, with density steps of 0.15/step.

    The step wedge was exposed so that several steps were all, 'max' black. Exposures were 16s at f/8 for unfiltered and magenta exposures, 64s at f/8 for yellow exposures.

    The incandescent bulb was a Philips Opal bulb, 160W, 4" diameter. The CFL was a GE FLE42HLX, 42W, 2700k, 82 CRI.

    I used an old Xrite densitometer to generate the curves, and in conjunction with a visual inspection to determine the first non-black step and last non-white step, determine the density range.


    ISO Range
    Yellow , No Filter, Magenta

    Inc Bulb 165 105 45
    CFL 150 45 45

    There appears to be a bump in contrast with a yellow filter at high paper densities, but with split grade printing, the yellow filter is normally used for the print highlights, and at those lower densities ,the curves are very similar.

    With no filter, the incandescent is approximately Grade 2, but the CFL is a grade 5 - suggesting that changes will be necessary to get intermediate contrasts with a single filter.

    I was expecting the CFL bulb spirals to cause a lighting evenness problem, but I did not see it on the step wedges.

    Things to do:

    Look at short exposure times, and bulb warm up/brightness issues.
    Make some real prints, and see if the spiral shape is an issue with the Durst 138 enlarger.
     

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  10. Nick Zentena

    Nick Zentena Member

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    Anybody try using a bluer bulb then the 2700s? Say the daylight ones?