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  1. #11

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    Quote Originally Posted by sanking
    In all of my tests I have never encountered a situation when Pyrocat_HD did not deliver full emulsion speed, even with the short developing times required for silver gelatin printing. And with AZO and alternative processes, which require a higher CI, my tests have always given much higher EFS values than rated emulsion speed.
    I should modify the above statement slightly. My tests indicate that Efke PL 100 and Bergger 200 do not deliver full emulsion speed with the 2:2:100 dilution of Pyrocat-HD.

    Sandy King

  2. #12
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    I must be doing something wrong then?

  3. #13
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    Leon,
    I wouldn't say your doing something wrong as I need to rate my fp4 at 64 when I print on AZO. One must keep in mind the varibles that can be encountered i.e. light meters, shutters, water temps, etc. I know when I work I do everything the same every time maintaining consistency throughout the whole process. Everything works together as a unit, thus if one thing is not "right" it will affect outcome. On the other hand if that one thing is not "right" every single time in your working system your results will be the same and not necessarily the same as what other people come up with.
    "EVERY film and paper is good .......... for something"
    Phil Davis

  4. #14

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    I am not saying that anybody is wrong. However, it is impossible to make meaningful comparisons of film speed (or speed in certain developes) based on field tests. Such tests involve not only variables in equipment (meters, lens apertures and shutters) but also in method and type of metering. And this is before we even bring the film to the darkroom for development.

    I completely eliminate these variable in testing for EFS by contact printing transmission step wedges with a light source timer by an integrator, which results in an error of less than 1/100 of a second with a 0.5 second exposure. Therefore the only variables in my testing are the film, developer (composition and temperature) and method of agitation. Of these the most important is method of agitation and I think many people would be surprised if they realized how even small differences in method of agitation can result in a significant change in contrast, and of EFS since there is a relationship between contrast and effective film speed..

    Naturally at some point you have to take the EFS values (what should be consistent from person to person if sound testing procedures are used) that results from testing and validate them in the field to give you a working exposure index, or EI. But EI is personal and can be expected to vary significantly because of the field variables mentioned.

    Sandy King

  5. #15
    roy
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    Quote Originally Posted by Leon
    I must be doing something wrong then?
    This does not follow. Rating the film at the speed you do may give you just the negative that suits the process in which you are working and your style of photography or subject matter.
    Roy Groombridge.

    Cogito, ergo sum.
    (Descartes)

  6. #16
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    ... point taken

  7. #17

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    I have found HD 1-1-100 to provide full film speed for FP4, HP5 (in sheet film) and Delta 100 and TriX in roll film.
    "Fundamentally I think we need to rediscover a non-ironic world"
    Robert Adams

  8. #18

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    Quote Originally Posted by sanking
    I completely eliminate these variable in testing for EFS by contact printing transmission step wedges with a light source timer by an integrator, which results in an error of less than 1/100 of a second with a 0.5 second exposure.
    You're not concerned with reciprocity at 1/2s exposures?

  9. #19
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    Most data on reciprocal trade disagreement is archaic. Howard Bond did extensive testing of a number of films and reported the results in Photo Techniques. I presented his data in a different form in a later issue. In a nutshell, 1/2 second is not significant
    Gadget Gainer

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