Contrast filter spacing

Discussion in 'Darkroom Developing and Printing' started by William Schneider, Jun 13, 2004.

  1. I have been curious about using an old Beseler PM2 color analyzer to read
    the color differences in contrast printing filters. Today I did some testing
    under my Aristo V54 cold lamp using both a Multigrade filter set (about 2
    years old) and a new set of Polymax contrast filters. I found that the
    Multigrade set did some odd things above the #3-1/2 filter. It would appear
    that the magenta/yellow balance in the #4 would REDUCE contrast when moving
    up from a #3-1/2, and appears to be tinted to produce contrasts below the
    #2-1/2 filter! Here's a link to a web page with a graph.

    I plan to use a step wedge to measure actual paper contrast with these
    filters, but before I undertake that lengthy exercise, I wondered if someone
    has had a similar experience. Do I have a set of filters that is labeled

    Polymax filters behaved like I would expect of a set of contrast filters,
    but the Ilford filters didn't. I'm looking for possible explanations before
    I get the next chance to dive into the darkroom again to sort through this

    BTW, the unfiltered Aristo V54 lamp reads +10 magenta if you wish to compare
    it to the filtered light readings.

    Bill Schneider
    William Schneider, Jun 13, 2004
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  2. There is an overall 1-stop density increase when going from a #3 1/2
    to a #4 filter, but I can't see how this alone would give the effect shown.

    I am taking it the filters look plausible and they visually
    progress monotonically from yellow to magenta - or do they seem to
    'back up' and turn yellowish again?

    If it is possible, I would like to see both the yellow and magenta
    readings plotted rather than just the difference.

    The only explanation I can offer is that the PM2 is at the
    limit of it's measuring range and the readings are becoming non-linear
    for the Ilford filter set.

    I don't have an Ilford set so I am sorry but I can not offer an
    independent set of readings.
    Nicholas O. Lindan, Jun 13, 2004
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  3. <<I am taking it the filters look plausible and they visually
    progress monotonically from yellow to magenta - or do they seem to
    'back up' and turn yellowish again?>>

    They do not progress smoothly in color, and there is indeed a reversing of
    color when viewing them. I had first attributed that to the ND in the
    filters to keep exposure constant, but it looks like the eyeball test was on
    the mark.

    I just made some test prints using a step wedge (they are still wet), and
    the #3-1/2 filter produces substantially higher contrast than the #4 does.
    Viewing them wet (and that will change a bit with dry-down), I count 9 steps
    using the #4 filter, and 6 steps using the #3-1/2 filter. The step wedge
    increment is 0.1.

    It looks like I need to get a new filter set, or at least re-label the
    existing filters in the kit.

    Bill Schneider
    William Schneider, Jun 13, 2004
  4. Fading?
    Michael Scarpitti, Jun 14, 2004
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