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  1. #1

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    Safelight testing with RA4 paper

    I have a DUKA safelight and while the Colorstar Analyser is extremely sensitive to extraneous light from a safelight I can have the DUKA quite bright and it passes the Colorstar test which is to take flitration and exposure readings with the safelight covered and do the same when uncovered and check to see that nothing changes.

    Well at the level I use my DUKA nothing does. I was about to assume that the safelight level I use was therefore OK from a fogging aspect but this may be an unwarranted assumption.

    So what is a correct test for RA4 paper?

    Thanks

    pentaxuser

  2. #2
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    There is no "correct" test. There is only a test that you can use for your own conditions.

    Measure the time it takes to make a normal print from package open to into the blix or stop (if open tray) or into the drum. Then place a strip of paper near your safelight, one on your easel, and one at the process site (protected from chemical contamination of course). Then, after exposure to safelight for the time interval measured above, go totally dark and process the 3 strips. Any fog should be compared to a 4th strip that was kept totally dark but is processed with the other 3 in the dark.

    Use a 5th strip that was blixed, washed and dried as the base reference.

    If there is fog, only you can determine if it is suitable for your purposes. A light tan fog about 0.02 above Dmin is probably ok, but any cyan fog is bad. This is what I have found. And, most safelights cause blue, cyan or purple fog.

    PE

  3. #3

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    Thanks PE . Is older paper that appears to be age-fogged more susceptible to safelight fog? I ask this because if it is then a test with suspected age-fogged paper might not give the true safe period that would the case with fresh paper?

    pentaxuser

  4. #4
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    Aged paper is no more sensitive to safelight fog than fresh paper, and if it has lost speed it is actually less sensitive!

    PE

  5. #5

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    Thanks PE I did a quick "coins on paper" test and it was clear that cyan fog was produced very quickly at reasonable light levels. It looks as if I need to re-appraise safelight levels and be prepared to operate in much darker conditions.

    Pity. The Nova Quad has some advantages over Jobo drum processing but putting a print into a Jobo drum in near total darkness is easier than using the Nova.

    Maybe I just need more practice in near dark conditions


    pentaxuser



 

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