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  1. #1
    Jon King's Avatar
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    Condenser Enlarger Illumination "evenness"

    I recently purchased a Durst L138S enlarger with a condenser head. My previous enlarger experience has been with color heads with a large diffused light source, so this is new territory for me.

    The bulb is a large (>4"/100mm dia)opal bulb. As I adjust the bulb location for the most uniform light distribution, the best I can do is to get the corners 1/3 to 1/2 stop dimmer than the center. Is this typical for condenser enlargers? I've read about light intensity variation with a condenser enlarger, but I've never seen any numbers to quantify the drop.

    The 138 has seperate condenser combinations for 5x7, 4x5 and 6x9, the combinations I have tried. My enlarging lenses are 180mm/150mm/100mm for the corresponding formats. Results are similar for each setup.

    Any suggestions, or am I doing ok with these results?

    Thanks,

  2. #2
    Jon Shiu's Avatar
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    Hi, I don't know the answer to your question, but was wondering if you are measuring fall off with a negative in the carrier, and if that would make a difference?

  3. #3
    Ed Sukach's Avatar
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    In a "collimated" (read: with condenser lenses) system, the classic method of alignment is to remove the lens, and adjust the lamp so that the filament is in the best possible focus and centered. When the lens is replaced the illumination will be the most even.

    It sounds (I'm sticking my neck in a noose a bit here - I am NOT familiar with the Meopta system) that the in-and out focusing (for want of a better description) is not quite at optimum - thus, a lot of fall-off at the corners.
    Carpe erratum!!

    Ed Sukach, FFP.

  4. #4
    Jon King's Avatar
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    Jon, I measured with and without the 5x7 glass carrier - it made no difference.

    Ed,

    I vaguely remember doing something like that with a microscope lighting system. I'm guessing the concepts aren't too far off. The lamp stage can move in 3 dimensions, and moving the lamp out(away from the condenser) seemed to help with the corners.

    I'm just not sure what 'good' is for a system like this. If this is as good as it gets, I'll stop messing with it and start using it. I'd evaluate it now by printing, except it is in the garage, and it is getting a bit cool at night to process prints!

    Thanks,

    Jon King

  5. #5
    Jon Shiu's Avatar
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    Okay, my idea was that the negative's base density would help prevent a hot spot from reflection or something, but you probably have no blank films to test with...

  6. #6

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    print eveness of illumination

    I use a Durst S45...a variation of the L138. I have not experienced uneven illumination. If you look at the diagram on the from of your enlarger head it shows the flat surface of the condensors facing down for the bottom condensor and up for the top condensor. This means that when the top condensor is installed the printing on the handle of the condensor will be upside down. Give it a try.

  7. #7

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    The correct choice of condensers will also depend upon the magnification desired. For a given format and lens focal length, there may be a couple of choices of condenser combinations for that reason. Make sure you're using the correct condenser pair for the magnification at which you're checking the illumination.
    My Verito page

    Anyone can appreciate a fine print. But it takes a real photographer to appreciate a fine negative.

  8. #8
    Blighty's Avatar
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    I have used a couple of condensor head enlargers (only medium format) and have always experienced a little light fall-off at the edges. It's just a matter of giving a little extra exposure at the edges to compensate. Regards, BLIGHTY.

  9. #9

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    jking,
    I'm not sure if this is possible with your enlarger but many years ago I had a condenser enlarger(beseler 23??) with a contrast filter holder directly under the lamp. In it I placed a piece of frosted glass to help diffuse the light and create more even distribution. Worked wonders and was very inexpensive. SatinSnow might even be able to help you out.

  10. #10

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    I've read of the Omega B22, a 6x6, that it does well with 35mm. Dan

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