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  1. #11
    dr bob's Avatar
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    On setting up my old Omega II, I had a bit of trouble getting even illumination with a 150mm lens, the proper extension cone, and a 4x5 carrier. The fall off was about one stop at the corners and edges. I finally traced the problem to the lamp position. I believe I remember that the “lamp source” (In my case it was a PH112, a standard size light bulb specially designed and frosted for enlarger use) should be focused on the entrance pupil of the lens with the condensers. (????)

    There is still a fall off but it is even and only about a half stop which can easily be compensated by “edge burning” the prints when necessary. The abandoned farmhouse in my gallery in an example of a print from a full-size 4x5 negative with the enlarger set up as discussed above without edge burn.

    Check your lamp position.
    I love the smell of fixer in the morning. It smells like...creativity!
    Truly, dr bob.

  2. #12
    lee
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    ask Don Miller he has 3 138's.

    lee\c

  3. #13

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    Be warned ;-)

    Hi !
    I own, and use, a Laborator 1000 which is the 4x5 version of the 138.
    The specs claims for a 65 mm opal lamp for negs up to 6cmx6cm and 100 mm above. Unfortunatelly, these are not made anymore. (it seems one can find 110 V version of the 4" bulb, at old new stock prices...)
    So I experienced severe light fall off even when using my C330 negs.
    First, I asked Durst Italy for a copy of the manual, which they provided free of charge ! Wonderfull service ! It helped me figure what condenser pairs I needed when using a 80 mm lens or a 105 mm lens for medium format, and have the correct condensers regarding enlarging factor. This helped even lighting on the baseboard but does not come close to perfection. So I went out shopping and to my delight found that Philips produced a big (95mm dia) bulb which is a double enveloppe high voltage 150 W halogen bulb ! Upon inspection, I found that the outer enveloppe is even, has no markings, and quite perfectly round. I tested it and this get to the right side but not spot on. So I placed a sheet of tracing paper in the filter drawer (which is between the lamp house and the 45 degree mirror above the condensers) and .... BINGO ! light was as even as I can dream of ! (measured with a RH designs Analyser Pro) ...
    So I went to the hardware store and bought a piece of glass used in fireplace doors to prevent the IR to cross ... I frosted it using engine grinding paste for valves, and here I am ... I have to add that this glass help keep flat the printing filters and help increase their life... (this is good because I am now unable to buy new ones, as Ilford has stopped making them.... (it seems they custom made the Kodak ones as well))
    Oh, BTW, I own the color head for this beast and I was given the cold light head. I do not like the color head (I think it is un practical to use variable contrast paper with it) and the cold light head is really diffuse, only blue so not good for the VC paper I use.
    hope this helps !

  4. #14

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    The correct bulb for the 138(S) is a 300W Atlas 3/16 type with aprox. 7.5"x4.5".

    You usually cannot prevent a little fall-off, but 1/3 stop seems too much. What is your exact condenser combination for which EL-lens at which aperture-setting?

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