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  1. #21

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    Quote Originally Posted by tomtom
    sandy - is your graph on unblinkingeye for bpf200 rated at 100asa? i sort of used those charts to figure out a development time but i rated my film at 200asa. now i'm not sure if my negs are fine or under developed or exposed :-?

    oh well, i'll be rating it at 100asa for now on :-)

    tomtom
    I have always rated BPF 200 at EI 100 for my testing. You can easily tell if your negatives are under developed. Just look at a shadow area (say about Zone II or III) and see if there is any detail there. If not, it was underexposed. If there is a lot of density in these areas you probably over exposed. Time of development has relatively little impact on shadow detail density so it is important to look her for signs of under or over exposure.

    Two others issues with BPF 200, and its sister films Fortepan 200 and JandC 200, is that they have a tremendous amount of development latitude and a relatively low CI at gamma infinity. In other words, you can develop the film over a wide range of times without significantly changing the contrast, or CI. The overall density of the negative increases, of course, but the slope of the curve stays about the same. This is a great feature in some respects because regardless of how long you develop the film you will still have a printable negative.

    A less positive way of stating the above is that films that have a lot of development latitude do not respond well to expansion and contraction development.

    And finally, it is especially important with this film to make your own tests because I have found different batches to be rather inconsistent in results, especially as regards how much contrast you can get out of the film. I have probably tested FP4+ over fifteen times over the past several years and the results from every tests are virtually identical. Of the eight or so tests I have done with BPF 200 and its sister films the results have been different virtually every time.

    Sandy King

  2. #22
    wdemere's Avatar
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    Sandy,

    I'm wondering if it would be worthwhile to include the EI with your times and curves in the article at unblinkingeye.com? - http://unblinkingeye.com/Articles/PCat/PCat4/pcat4.html

    Also, I think it would be helpful to add the times into the general film development times that are kept there if that is possible:

    http://unblinkingeye.com/Articles/Times/times.html

    Last night, for example, was the first time I developed Efke 100 in pyrocat-hd. I found a time of 16.5 minutes at 21degreesC with 30 sec then 5 sec at halfway by searching on google. That worked, but I had exposed at EI100, and it is obvious that I need to try EI50 as the negs came out underexposed but developed OK (120 rollfilm).

    For minimal agitation, it might be nice to list times too, or at least indicate a percentage to increase.

    If you need someone to edit the html or compile the times I would be happy to assist :-)

    Of course, I understand that everyone should test, but given that pyrocat-hd is becoming a very popular developer it might help a lot of new users get started.

    Thanks,

    William
    "I know of no country in which there is so little independence of mind and real freedom of discussion as in America." -- Alexis de Tocqueville

  3. #23

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    Quote Originally Posted by wdemere
    Sandy,

    I'm wondering if it would be worthwhile to include the EI with your times and curves in the article at unblinkingeye.com? - http://unblinkingeye.com/Articles/PCat/PCat4/pcat4.html


    William

    The problem I see with this is that people have such widely different ways of meteting and determiing personal effective film speed values that the information I derive from sensitometry would not be particulary useful in a practical context.

    Film contrast is another issue because if you develop the same way I do using the same film you should get the same results. That is why I am more confortable posting results for film CI than for EI.

    Sandy

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