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  1. #1
    Eric Rose's Avatar
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    Reading charts on PyroCat-HD

    Ok I'm challenged. I admit it. But I have no idea what the heck Sandy is trying to convey on these charts. http://unblinkingeye.com/Articles/PCat/PCat4/pcat4.html

    What the heck is the "G" axis?
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  2. #2

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    Eric, rather then taking a chance on misinforming you, the link below may give you the information that you want. Good luck.

    http://www.btzs.org/Articles/HowToReadFilmTest.htm

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    Donald,

    Thanks for posting the link. Knowing of its existence will save me a lot of time in answering questions about some of the BTZS type charts I ocassionally use or reference in my writings.

    Sandy




    Quote Originally Posted by Donald Miller
    Eric, rather then taking a chance on misinforming you, the link below may give you the information that you want. Good luck.

    http://www.btzs.org/Articles/HowToReadFilmTest.htm

  4. #4
    Eric Rose's Avatar
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    Thanks guys it was great reading. but I still can't figure out how I can use this information to determine what deveopment time I need for FP4 rated at say 100asa. Or 125, close enough.

    If a person could get a copy of the full set of charts for 1:1:100 that would be fantastic.
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    Quote Originally Posted by Eric Rose
    Thanks guys it was great reading. but I still can't figure out how I can use this information to determine what deveopment time I need for FP4 rated at say 100asa. Or 125, close enough.

    If a person could get a copy of the full set of charts for 1:1:100 that would be fantastic.

    Eric,

    If you want to develop FP4 for silver then the CI would fall into .47-.52. (first table in the Unblinkingeye article). Then if you go down to the chart for FP4 developed in Pyrocat 1-1-100 read with the blue channel of the densitiometer (figure 16) you will see that the time looks to be six minutes at 70 degrees.(CI---.5) I believe that these tests are done with BTZS type tubes or on a motor base...Sandy normally does his tests using those means of agitation. If you use tray development, I would add about 20% to the indicated times.

    The UV channel reading would be for those processes or paper that are exposed through UVA light sources. Not typically silver. Hope this helps.

  6. #6
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    Awesome! Thanks Donald. Hey are you coming to the conference? One more question. Isn't there always LOL. I have been developing 6 - 4x5 sheets in 1300ml of solution and getting consistantly thin negs with PC-HD. What I have been doing is using 13ml of both solutions A and B then adding water to bring it up to 1300. I hope this is 1:1:100. Is this to much surface area for the amount of working A&B I am using? Or maybe I'm just mixing it wrong.

    I have been using 20C for temp, 8 to 9 minutes for development time (creeping it up), 15sec initial agg. then 10 sec every minute until done. Water stop, and Ilford fix.
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  7. #7

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    Quote Originally Posted by Donald Miller
    Eric,

    If you want to develop FP4 for silver then the CI would fall into .47-.52. (first table in the Unblinkingeye article). Then if you go down to the chart for FP4 developed in Pyrocat 1-1-100 read with the blue channel of the densitiometer (figure 16) you will see that the time looks to be six minutes at 70 degrees.(CI---.5) I believe that these tests are done with BTZS type tubes or on a motor base...Sandy normally does his tests using those means of agitation. If you use tray development, I would add about 20% to the indicated times.

    The UV channel reading would be for those processes or paper that are exposed through UVA light sources. Not typically silver. Hope this helps.
    Donald is right about the type of agitation I use for testing film. Another thing to consider is that my development times are calibrated to graded silver gelatin papers. For VC papers you should add about 30% to the time indicated by the chart. If you make the adjustment you will have a time that should be useful for initial testing of most film/developer combinations.

    Sandy

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    Eric Rose's Avatar
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    I forgot to mention I use a tank and hangers. From my limited understanding of using tubes the times are quite different. Is there a general rule of thumb for the conversion?
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    Quote Originally Posted by Eric Rose
    I forgot to mention I use a tank and hangers. From my limited understanding of using tubes the times are quite different. Is there a general rule of thumb for the conversion?

    Eric,

    Since I have not used tanks and hangers before, I don't know how much the agitation differs from tube and motorbase agitation...I would assume that it was less but I may be wrong...if I were in your shoes I would probably start my testing at about 9 to 9 1/2 minutes for pyrocat 1-1-100 at 70 degrees on FP4 if you are printing on VC paper. That should get you into the ball park.

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    To answer Eric's original question, different printing processes require different sorts of negatives for best results. Mostly, this can be reduced to different contrasts. The table in Sandy's article lists several different printing processes (conventional silver-gelatine and several alternative processes) and his conclusions for the best negative contrast index (CI) to use for each of them. The charts plot development time against gradient (G) for several films. While not exactly the same, CI and G measure contrast in similar ways. Here they can probably be used interchangeably.

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