A question on enlarger column elevation

Discussion in 'Enlarging' started by stormbytes, Jan 12, 2008.

  1. stormbytes

    stormbytes Member

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    I'm in the process of re-testing my films after an extended absence from Photography. Ironically, I'm still baffled by many of the same questions that haunted me in the earlier years.

    Reminiscing Fred Picker's "Zone VI Workshop", he would test film/development (for Dmax) on a specific paper AND at a specific column elevation. Is this correct? Or can we safely assume that a negative will print with the same contrast at ANY elevation given that the density values (highs:lows) remain in constant proportion?

    Thanks for the help!
     
  2. Dan Henderson

    Dan Henderson Member

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    I can't think of any reason why enlarger height would affect contrast. As you say, raising the enlarger will affect overall density in equal proportions, thereby keeping contrast the same.

    Dan
     
  3. fschifano

    fschifano Member

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    Assuming that the same lens is used with the same enlarger at the same height and aperture, the variables of lens flare, spill light from the enlarger, etc. are kept to a constant value. A change in any one of these variables can introduce a change in contrast of the final print. Print contrast can't be quantified if all the variables going into it are moving targets.

    For a concrete example, select a negative and make two prints from it. Make one at 4x and another at 8x using the same paper with the same contrast filter. If using graded papers, use two pieces from the same batch. Which one has more apparent contrast. Subjectively, the smaller print will have more "snap" to it.
     
  4. David H. Bebbington

    David H. Bebbington Inactive

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    Enlarger height would not affect contrast if you had an enlarger head where you could vary the light intensity and always print at the same exposure time. If, however, like most people, you increase exposure for bigger prints, reciprocity law failure of the paper comes into play and effective contrast will increase as the prints get bigger. Try making a 5x7" and 20x30" print from the same neg and you will soon find it's really hard to hold the contrast on the big print to the same value as in the small one!

    Regards,

    David
     
  5. CPorter

    CPorter Member

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    A change in enlarger height will mean a change in exposure time to achieve the same print values you had before you moved the enlarging head. So, a change in height is a change in all print values unless adjustments are made for time.

    The column height with regard to what Picker was writing about is in reference to obtaining the minimum exposure time in the enlarger (through Zone 0 i.e., clear film base) to produce maximum black on the paper or Dmax. Finding the minimum time through clear film is how he suggested you can " visually" determine if the Zone 8 negative density was correct or close for "Normal" dev time by evaluating a Zone 8 print tone.

    To do that effectively, you must use the same enlarger height so that your print times do not change when going from the zone 0 negative to the zone 8 negative. Ex: If the minimum time is 15 sec for Dmax through Zone 0, then you would place the Zone 8 negative in the enlarger expose it for 15 seconds, the resulting print tone should match a verbal description of Zone VIII. According to Picker, that would be "a slight tonality barely darker than....pure white."