Evaluation of film, developer, and enlarger light source

Discussion in 'Darkroom Equipment' started by Donald Miller, Feb 26, 2006.

  1. Donald Miller

    Donald Miller Member

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    I have been reprinting a lot of old and new negatives during the past week. This is the first time that I have had the opportunity to evaluate Tri X developed in HC 110, Efke PL 100 developed in Pyrocat, and Bergger BPF 200 developed in Pyrocat with my point light source enlarger. The Pyrocat developed negatives were developed in both semi stand and continual agitation with tubes. The Tri X negatives were tray developed.

    I recently designed, built and installed a point light system for my Durst 138S condenser enlarger and this seems to level the playing field a lot more between the different films and developers. I have to say that for my work that Efke PL 100 in Pyrocat is a clear winner in terms of local contrast and sharpness. The Tri X developed in HC 110 has a smoother tonal response. Because of the greater local contrast in the Efke negative, the Efke print has the appearance of being much sharper.

    Surprising to me is that I could tell no difference between a continuous agitated Efke PL 100 print from a semi stand (minimal agitation) print when enlarged 3X. Both prints are very sharp. The camera lens (Symmar S 210mm) was the same in both cases of the Efke prints.
     
  2. avandesande

    avandesande Member

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    It would be a nice idea if someone put together an article on point source. I have a lot of interest in it but I haven't been able to find out anything about it on the web.
     
  3. resummerfield

    resummerfield Subscriber

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    Donald, are you using the coated condensers or the regular condensers in your point light system?
     
  4. Donald Miller

    Donald Miller Member

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    I am using the regular condensers and the regular mirror. Seems to work great. I can't compare it to the coated items but it is such a big improvement over the opal lamp...at least in my experience.
     
  5. egdinger

    egdinger Member

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    Could you do a write up on how you did the conversion, I have a different durst that I may want to convert.
     
  6. Donald Miller

    Donald Miller Member

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    I would like to accomodate you but it isn't quite so simple. The problem is that the design of the reflector utilized is complex and quite specific insofar as the radii and their position. Thus while the general theory is transferable, the specifics are not.

    The problem that presents itself when moving from a roughly 4 inch diameter heavily frosted globe (300 and 500 watt Thorn lamp in the case of the 138S) to a very small filament in a 3/4 inch clear envelope is even light distribution.
     
  7. avandesande

    avandesande Member

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    The new blue high intensity LEDs may be a novel way to do this. They are also highly directional so you wouldn't need a reflector.
     
  8. Donald Miller

    Donald Miller Member

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    I initially thought that it was as simple as positioning a lamp but it isn't that simple. I use a 1000 watt lamp.