Speed Matching Filters

Discussion in 'Enlarging' started by CPorter, Mar 29, 2004.

  1. CPorter

    CPorter Member

    Feb 2, 2004
    West KY
    4x5 Format
    Hi All,

    I've been reading up (i.e., Steve Anchell's book: The Variable Contrast Printing Manual, copyright 1997) on determining the relative printing speed between the filters in my Kodak Polymax filter set (I use PolymaxII paper). I have noticed that there are some wierd differences between the some filters, most notibly between grade 2 and 3 filters; meaning, that there seems to be a much greater difference in the progression of contrast between 2 and 3 than between other grades.

    So, I'm wondering if any of you have ever performed such a test as he begins to describe on page 45 of that book (if you have it to refer to)? I'm referring to the "Filter Exposure Factor" chart that he recommends for quick exposure calculations when changing between filters. If I'm reading this correctly, then a successful development of that chart will provide me with the means to correctly speed match my filters for the enlarger/light source that I'm using (Omega B-8 with an Aristo cold light, v-54 lamp).

    If any of you have done this test, is there anything that you can tell me to be careful of, or otherwise help me make sure that I don't waste a lot of paper in the process trying this test.

    Thanks for any helpful comments.
  2. MSchuler

    MSchuler Subscriber

    Oct 20, 2004
    Multi Format
    I actually just did this test myself, using Ilford filters and paper. I also noticed that the contrast I got was not even across the filter set. Last night I threw together an Excel spreadsheet into which I plug my visual observations, to calculate the chart that Anchell illustrates, or so I hope. It still needs a bit of cleaning up.

    The only thing I noticed was that I wish I would have bought a 41-step step wedge instead of the 21-step one. Oh, and that step 11 appears on both sides of the Stouffer step wedge - didn't catch that until I got done counting steps.

    I'll report back if I find anything else out when I compare these results to the Oriental Seagull test I'm going to do this weekend.