Hotspot with Photolux bulbs?

Discussion in 'Enlarging' started by batwister, Apr 5, 2012.

  1. batwister

    batwister Member

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    I've just bought my second Photolux bulb after thinking the first was defective. Both have given me a prawn shaped hotspot which is completely unworkable. It's visible with and without the condensers - tried with both 35mm and 6x6. With another bulb however, which has a thicker coating, the light is completely uniform but the exposure times are running into a minute or more.

    The enlarger is a Krokus 3.
     
  2. michael_r

    michael_r Subscriber

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    Before I switched to diffusion enlarging I found I had a very hard time getting decent quality replacement bulbs for my old Omega condenser enlarger (it used a 75w - I think PH140?). I found it increasingly difficult to get good names like GE etc for stuff like this, even when ordering online or talking directly to specialists and distributors. I ended up mostly with shit EIKO or whatever other crap from China and the opal coatings were always garbage, never uniform, with hot spots, concentric circles and other things showing up on the baseboard.
     
  3. MartinP

    MartinP Member

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    Aren't Photolux bulbs for illumination, not for in enlargers? I've not had any problems with Photocrescenta bulbs anyway. Those are the usual white enlarger bulbs - if you have something which is a translucent grey (similar to a standard opal household bulb) then it was intended for use in some sort of tungsten lighting fixture, not an enlarger.
     
  4. Worker 11811

    Worker 11811 Member

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    I don't know your enlarger but I am wondering whether the lamp house is focused correctly.

    Does your enlarger have a prefocused lamp? If so, that's probably not the problem. Otherwise, check the lamp socket to be sure it is aligned correctly so that it produces even light.

    Secondarily, check to be sure the lamp is inserted into the socket correctly. If it doesn't fit right, it won't position the filiament in the focal point of the reflector.

    After that, as others say, the lamp you have chosen might not be up to spec.