What's up with my cold light head ( or VC filter problem)

Discussion in 'Enlarging' started by nze, Feb 10, 2006.

  1. nze

    nze Member

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    Hello all

    Last week I decide to try some VC Paper, you should consider me as a Graded paper fanatic. But I hear of the split grade printing method and I want to give it a try.

    I have an old Durst 1000 with condenser light and Durst cold light head which I almost use. With my graded paper I get 10-20 seconds exposure for most of my work and I fine control the contrast with pre exposure, and developper.

    But My problem with VC paper (I try Bergger which need long exposure time) is that for grade 2.5 to 5 I need about the same printing time but for grade 2 and under my printing time are far longer and worse than all exposure is different at each change of filter. for example for grade 1 I need to expose 40 second and then for 00 60 seconds.

    I already use filter with cold ligth ( about ten years ago) but I never got such problem.


    Regards
     
  2. David H. Bebbington

    David H. Bebbington Inactive

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    As I am sure you know, you need to expose VC paper with yellow light to get low contrast. Some "cold-light " (cold cathode) heads are so blue that you cannot use VC paper at all, more modern ones are better but may still be bluish so that exposures through a yellow filter are disproportionately long. If you have the option of printing with a condenser head, this would be much better.
     
  3. nze

    nze Member

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    I think mine is so blue .
    You well write what's happen to me. In fact he last Cold light head I've used was a Zone VI and I never got such problem.

    I will go back with the condenser light and the yellow bulb to use this paper.

    Thanks
     
  4. vet173

    vet173 Member

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    I don't remember where I read it, maybe here? On some coldlights you need a green filter on light source to change the blue output enough to use VC papers.
     
  5. Bob F.

    Bob F. Member

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    With older cold light heads (specifically with the Aristo W45 lamp), Ilford recommend a 40Y filter with MGIV. PDF labelled "CONTRAST CONTROL" on the Ilford site here: http://www.ilford.com/html/us_english/bw.html


    Cheers, Bob.
     
  6. papagene

    papagene Membership Council Council

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    Those times you stated are normal for me, depending on what film, film size and how they were developed. I use a 40 ccy along with the VC filters and believe that that combination is the reason for my times.
    Good jazz playing on my little boom-box is enought to distract me so that I don't notice the longer times. :D

    gene
     
  7. George Collier

    George Collier Member

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    Aristo now makes a V54 lamp for their heads which is a more blue-green color, balanced for VC filters. I use one, and do experience longer exposures, but with Forte Polygrade V FB it is worth the trouble, for me. Also, the information with the filters (I use Ilford filters) states a uniformity of exposure between most of the grades (except the extreme ends), which does not happen even with Ilford MG paper, I assume because of the light color. I still use the combination above and find it worth occasional total exposure time of 5-7 minutes (4x5 enlarged to 16x20 - including two filter exposures and some burning in) for the results I get.
     
  8. nze

    nze Member

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    Thanks for your answers

    I will look for a 40ccy for my cold light, as most of my neg are developed for it. and I put back some miles davis or fela kuti songs in my lab

    total exposure time of 5-7 minutes
    That's quite a long exposure as my Platinum print but I may appreciate this way of work. Should give it a try

    best
     
  9. nze

    nze Member

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    I 've jsut check the Ilford PDf and find interesting information about recalculating time when using cold light head with 40y filter . and also how change the cntrast with the use of the cold light head.
    Thanks again
     
  10. RJS

    RJS Member

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    I use an Aristo V54 cold light head in a Beseler. 8X10 printing times (from 4X5) run about 3 swconds. I mad a set of exposures using a calibrated step wedge fromStouffer, increments of half a stop, and found that I get a full range of contrast, including 5, according to the numbers in Steve Anchell's book on VC paper. This with Ilford MG fiber paper. I use a rheostat Aristo sells to attenuate the light; to ge the 3-4 second exposure above I cut the light 21/2 stops from f5.6. So I am delighted with this setup.