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  1. #31
    Bill Burk's Avatar
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    markbarendt,

    So Stephen meant there is no exposure constant (0.8 in the numerator of the speed formula). But you are also right, there is no safety factor.

    Also there is no K. Flare is included. Many of the factors are merged into the procedure and cannot be broken out individually.

    Doremus Scudder,

    Now you're talking my language! We need the technical, but it also needs to be translated to non-technical.

  2. #32
    Bill Burk's Avatar
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    I forgot to mention... If you test with Tungsten lighting, and your meter is overly sensitive to red wavelengths... While your film is "more or less" sensitive to near infrared... Then your "speed" will be lower than ISO [meter needle is higher than it should for the actinic light] and the Tungsten "speed" difference from Daylight may vary between different films of the same ISO rating. This is because meter spectral response may depart from film spectral response. The Zone VI modified spotmeters are intended to correlate well to Tri-X - so if you have one of those, then your tests may correlate better. But change film to a tabular grain type film and the correlation may not be the same. I've tested 400 TMAX and find it can take a very long exposure to a near infrared (visible to the eye) red LED with little fog.

  3. #33

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    It is worth noting many ZS testers just try to find a net D of 0.1 4 stops below metered without giving more thought to local contrast in the toe. 0.1 above B+F in the context of the ZS is a means to an end, the end being adequate shadow contrast, which is subjective to some extent. A target Zone I density in and of itself is meaningless.
    Last edited by Michael R 1974; 03-10-2013 at 03:15 PM. Click to view previous post history.

  4. #34
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    This thread makes me wonder if the 18% grey card issue is really the source of the apparent problem.
    We have heard many times about how midtone does not get truly exposed to be mid-tone unless adjusting up the 18% grey card reading per Kodak's instructions. Put in other terms, reading a 12% grey card probably puts midtone closer to middle of the range!

  5. #35
    Bill Burk's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    It is worth noting many ZS testers just try to find a net D of 0.1 4 stops below metered without giving more thought to local contrast in the toe. 0.1 above B+F in the context of the ZS is a means to an end, the end being adequate shadow contrast, which is subjective to some extent. A target Zone I density in and of itself is meaningless.
    That's a very important fact. The 0.1 Density for Zone I came later. First it was a noticeable difference between blackest black and first detectable tone. Ralph Lambrecht pointed out in the Focal Encyclopedia that later papers were able to reach such a higher D-Max that even the earlier visual match test became unreliable.

  6. #36
    Bill Burk's Avatar
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    Quote Originally Posted by wiltw View Post
    This thread makes me wonder if the 18% grey card issue is really the source of the apparent problem.
    We have heard many times about how midtone does not get truly exposed to be mid-tone unless adjusting up the 18% grey card reading per Kodak's instructions. Put in other terms, reading a 12% grey card probably puts midtone closer to middle of the range!
    If you meter a gray card and attempt to make its tone appear 0.1 density on the negative (or visual match in shadows), then you aren't using it as anything but an arbitrary gray.

    The 18% gray issue isn't really a big problem for Zone System tests, though it is an important issue relevant to other metering and exposure topics.

  7. #37

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    You customize film speed relative to your own specific development method and what you consider as
    acceptable film performance relative to your own "normal" lighting conditions. There are no hard rules.

  8. #38
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    For ZS users film speed is very simple and I have always used it. Ansel said Z1 is .1 over base fog as you have noticed. Exposure and development for Z1 is the least flexible of all the tones. For some reason box speed usually won't allow you to achieve .1 over base fog. If Ansel had said that zone 1 density should be .05 above base fog then box speed would work and people would just place their tone desires at a higher zone.

    Using the Zone system everything becomes relative to what you want your prints to look like. It all becomes subjective. Ansel could just as easily said that Z1 should be .2 above base fog and then everyone would have changed how they place their shadows. I was taught to use .1 over base fog and so I place my shadows up around Z3 depending on the situation. Once you have established your normal development for Z7 or 8 and have that contrast look fixed in your mind then out in the real world with your spot meter you are trying to visualize what you want for contrast. Where you want detail and where you don't.

  9. #39
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    Would it be fair to say the ZS target is the point where the first excellent print can be made?
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  10. #40
    Stephen Benskin's Avatar
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    Quote Originally Posted by markbarendt View Post
    Would it be fair to say the ZS target is the point where the first excellent print can be made?
    The fixed density 0.10 over Fb+f is about 0.29 log-H to the right of the first excellent print judgment speed with normal development.

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