Durst 1000 - Blue filter

Discussion in 'Darkroom Equipment' started by SMBooth, Aug 27, 2012.

  1. SMBooth

    SMBooth Member

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    Ive put together a darkroom, my 'new' enlarger is a Durst 1000 with condensers and bulb which requires a filter set for contrast. I'm curious to know why previous user inserted a blue filter between the lamp and condenser. Should I remove it to get correct contrast filtering or does the blue filter improve something I don't know about.
     
  2. Chris Lange

    Chris Lange Member

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    it's supposedly better to focus with blue light because that is the color that photographic papers are traditionally sensitized to see. focusing with white light, in theory, is less accurate because the different wavelengths of light focus at different distances.

    that said, in practice, I have never seen a difference.
     
  3. SMBooth

    SMBooth Member

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    I did read after posting that a blue filter will reduce contrast when using a condenser enlarger setup, but that was Popular Mechanics.....
    I guess I'll do some step wedge tests tonight.
     
  4. MattKing

    MattKing Subscriber

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    A blue filter would increase contrast with variable contrast paper. Is the light source quite green or yellow without it?
     
  5. SMBooth

    SMBooth Member

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    No its a typical white photo 150 watt photo lamp for enlargers. Printing tonight with it seemed OK. I have not put the step wedge under it yet.
     
  6. Michael R 1974

    Michael R 1974 Subscriber

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    I can't think of a good reason to leave the blue filter in. The blue/focus thing is baloney. As for contrast, it would theoretically give you maximum contrast with VC paper (although it depends on the specific spectral sensitivity of the paper and spectral transmission of the particular blue filter. Printing speed will be reduced to varying degrees. With graded paper the only effect would be reduced printing speed.
     
  7. munz6869

    munz6869 Subscriber

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    I have a blue filter accessory for my Grain focuser, and folks have often commented how sharp my prints are... Of course I have never ever used the thing (and why would I? It just makes everything annoyingly darker!).

    Marc!
     
  8. ath

    ath Member

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    Last edited by a moderator: Aug 28, 2012
  9. Michael R 1974

    Michael R 1974 Subscriber

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    Neither a heat absorbing filter nor or a UV absorbing filter would have a visible blue color. (A UV filter wouldn't be blue anyway). Putting a visible-spectrum blue filter in the light path can only interfere with VC contrast control as a blue filter will attenuate green light.
     
  10. ath

    ath Member

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    The heat absorbing filters I know have a greenish-blueish cast. Maybe the OP could comment if the filter has a colour cast or a strong distinctive colour?
     
  11. Michael R 1974

    Michael R 1974 Subscriber

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    Good point. I was picturing a really blue looking filter but perhaps it's just a slight tint.
     
  12. ath

    ath Member

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    OTOH if the filter is a colour conversion filter (i.e. a KB3 or so) the former user might have tried to enhance contrast. A frosted bulb with 150W says nothing about the colour temperature of the light; maybe it's not a dedicated bulb for enlargers and the spectrum is simply to warm.
     
  13. SMBooth

    SMBooth Member

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    No bulb is a Phillips Photocrescenta PF 605, filter is pale blue not unlike a 82C filter. It not heat glass its tape directly to the top condenser.
     
  14. ic-racer

    ic-racer Member

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    Obviously there are thousands of irrational reasons the filter could be there. If you are interested in some rational reasons, I can suggest the enlarger may have been used as a sensitometer.
     
  15. Poisson Du Jour

    Poisson Du Jour Member

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    My understanding is you're not kitted out for colour printing (correct me if I'm wrong), but maybe the filter was to provide a slightly cooler light to the warmer/reddish lamp? Much the same as you'd use an 82 A-B-C filter to cool down an overly red scene. Another theory is to correct for visual colour deficiency ("colour blindness"), much the same as a few people where blue-tinted glasses, others still wear rose-tinted... there are likely thousands of reasons.
     
  16. johnnywalker

    johnnywalker Subscriber

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    My experience as well.
     
  17. ath

    ath Member

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    The bulb seems to be the correct one. The fact that the filter is taped to the condensor shows that it was not intended by DURST. Just remove it.
     
  18. Steve Smith

    Steve Smith Subscriber

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    Gene Nocon recommended the blue filter in his book Darkroom Printing. He suggested that it was better to focus using the same colour of light which the paper is sensitive too.

    It doesn't matter if the light is filtered at the source or at the grain focusing device but I would remove it from the enlarger to make an actual print.


    Steve.
     
  19. RalphLambrecht

    RalphLambrecht Subscriber

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    please report your findings. i would be surprisedif it does anything but reduce light intensity.
     
  20. SMBooth

    SMBooth Member

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    Did a test using some ilford RC paper, grade 2.5 filter, 25 sec exposure each with the blue filter in and out, really not any different. I think you are right Ralph.