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  1. #1

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    Testing for relative ISO Range numbers

    I have Hansa HC-2000 dichroic color enlarger with 100W bulb and Kodak Polycntrast filters. Though, the enlarger has colorhead with dichroic filters, I tried to test for relative ISO Range numbers with gelatine polycontrast filters. The test procedure has been as descibed in Steve Anchell's Variable Contrast Printing Manual using Stauffer 21-step density tablet in the negative carrier. I use Ilfod MG glossy papers.Though, the procedure recommends starting point of f/8 at 10 seconds, I could get three white steps at f/4 and 100 seconds with -1 filter and with this setting the the last three steps do not become maximum black as required, they continue to be dark greys. So what is wrong- my testing procedure or the equipment ? I shall appreciate your help. Hansraj.

  2. #2

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    Quote Originally Posted by Hansraj Vyas View Post
    ...three white steps at f/4 and 100 seconds with -1 filter
    and with this setting the the last three steps do not become
    maximum black as required, Hansraj.
    As required? Three white steps and three not so black
    black steps. Out of 21 steps that leaves 15. That makes
    for a ES of about 2.25; off the scale on the low end.

    Test with no filtration. None. With that paper you
    should see 7 plus steps and that with a whole lot less
    than a 100 second exposure.

    Just how do you count steps. I've read an article by
    David Vestal where in he relates his method,
    edge counting. Dan

  3. #3

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    Testing for relative ISO numbers

    As mentioned by me, the test has been carried out as detailed in the book The Variable Contrast Printing Manual by Steve Anchell-pages 39 and 40. He states-There should be atleast three paper base white steps before the first signs of density change.He also states further that there should two or more inseparable maximum black steps at the other end. I feel that dichroic colorhead needs longer exposures since with my condenser enlarger the exposures used to be quite short. Hansraj.

  4. #4
    Bob F.'s Avatar
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    I have no idea how that method works, not having a copy of the book. However, I have used a step wedge to test paper in the past and getting 3 steps before you start to get some tone and then not going black long before it reaches step 21 suggests a major problem somewhere. Some possibilities occur: are you leaving the print to fully develop? Fibre will want at least 2 minutes in most developers, 3 or 4 minutes in some (especially warm tone developers) would not hurt, and is the developer fresh?

    How large an image are you projecting on to the paper: that may explain the long times. You don't really need more than about x2 magnification which should be only a few seconds, even with a diffusion enlarger.

    I put dots on the wedge alongside the steps to make it easier to see where each step is later.

    Good luck, Bob.

  5. #5

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    Testing for relative ISO range numbers

    Thanks, Bob, for your response. The developer is a couple of months old but properly stored and not turned brown at all. The enlargement is 4x5 size- just large enough to read the steps properly. The diffused light source is a Xenophot HLX 100 W bulb. I agree. something is certainly wrong somewhere. Anyway, I will continue to search. Regards, Hansraj.

  6. #6
    Bob F.'s Avatar
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    Probably worth checking the paper. Get a test piece of paper out of the pack in the dark and then switch the lights on and pop it in the developer with the room lights still on to check that it does go fully black. If it only goes grey then try fresh developer before blaming the paper as it's more likely to be a chemical problem. If it does go black, then you are back to square one unfortunately...

    Cheers, Bob.

  7. #7

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    IIRC the test is basically stick the step wedge on the paper some how. Either in the neg carrier or on the paper if you contact print. Expose. process. Dry. Then you count the number of wedges between full black and full white. You compare this number with the chart to get an ISO contrast grade.

    If the question is you're having a hard time getting the -1 grade to go black but the other grades are working fine? If that is the question then I'd guess everything is fine. If you had a developer problem it would have shown up with the other tests to.

    When I did the test I found I could go very low in contrast. The issue was the high end. I could get just over grade 4.

  8. #8

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    Testing for relative ISO numbers

    Thanks Bob and Nick for your replies. I will make one more attempt. Regards, Hansraj.

  9. #9
    Bruce Osgood's Avatar
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    I am not familiar with Steve Anchell's Variable Contrast Printing Manual using Stauffer 21-step density tablet in the negative carrier. But I have been doing it today with Forte Polywarmtone +.

    With the Stauffer 21-step tablet in the neg carrier and elevated to cover an 8X10 sheet of PWT+ paper I got an unfiltered exposure of 25.2 seconds to produce a first discernable black contrast at step 4 and paper white at step 15. I've been using an E-72 developer for two minutes and it works quite nicely.

  10. #10

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    Testing for relative ISO numbers

    Thanks, Mr.Bruce for your reply. Hansraj.



 

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