Calibrating an Old Dichro DG Beseler Color Head Questions

Discussion in 'Darkroom Equipment' started by JeffD, Mar 15, 2006.

  1. JeffD

    JeffD Member

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    Long post, but thanks if you are able to follow along!

    A while back I made an attempt to calibrate my old Beseler Dichro DG colorhead to my particular printing materials.

    I did a series of projection prints of a stouffers 21 step wedge onto 4x5 sheets of papers, and various filtrations, and tried to make a curve of the resulting contrast range vs. the changes in filtrations.

    Recently, reading an Ilford data sheed for multicontrast paper makes me think I may have made a mistake.

    I started my wedge print series with a maximum of 130 units of yellow, no magenta, and decreased my yellow by, I think 20 units per print, then continued on with 0 units of yellow, and steadily increasing magenta.

    The curve was somewhat irregular, but gave me enough data to figure rough approximations of equivalent paper grades. Now I'm thinking I could have done better...

    The Ilford data sheet I read suggested yellow and magenta values to achieve grades using two different Durst heads, a kodak value, and a Leitz Focomat V35.

    My questions:

    Does my Besler DG Dichro use the equivalent of "kodak" filtration values?

    Also, my testing didn't mix yellow and magenta, but used only varying amounts of either one. The Ilford data sheet seems to recommend combinations of both Yellow and Magenta. Is this only to keep the speed point similar, or is there other reasons?

    [update- a close look at the data sheet implies that using both colors, though requiring longer exposures, keeps the exposure times closer together for different grades.]

    Do most of you mix these two values in different ratios, or use either Yellow or Magenta only, but in varying amounts?

    I guess this would explain my not so smooth curve in my plots of the contrast range vs change in filter values, described above?
     
  2. glbeas

    glbeas Member

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    You are right, the mix of colors are producing "neutral density" values to keep the exposure times consistant from grade to grade. One of several ways to use the color head with VC. What you were doing is another, split filter printing is another - sort of an additive process. They all work, just depends on how much work you want to do to get it.I have a DG head, but I took it off in favor of a condensor head. I used to do it similar to what you do, using a PM2 analyser to set the exposure levels.
     
  3. JeffD

    JeffD Member

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    Hey Gary- are you using the standard non dichro head condensor for your Beseler? I have that, but was attracted by a cheap dichro I found at Wings camera used. Are you using the filters in a tray, or not using filters?

    I have a pretty nice analyzer from RH Designs that helps me with the exposure times, so I don't really care about keeping them the same with neutral density values.
     
  4. glbeas

    glbeas Member

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