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Thread: BTZS, Zone System, Everyone Else... Film Speed ?

  1. #21
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    Re: BTZS, Zone System, Everyone Else... Film Speed ?

    There's nothing in the zone system that says the "real" film speed is 1/2 the box speed. The film speed is determined by testing. It might end up being 1/2 the box speed or it may not.

    True enough. But isn't it a rather unusual "coincidence" that after testing, most people arrive at the same basic adjustment ?

    I learned the Zone System from Fred Picker around 1970. Ansel had tested Tri-X + HC-110 and determined a film speed of 250. Fred did his own tests, and determined a speed of 250. I did my own tests and determined a speed of 250. It makes sense after all: we were all testing the same film and developer combination, doing the same basic agitation, with a decent thermometer, etc.

  2. #22

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    Re: BTZS, Zone System, Everyone Else... Film Speed ?

    Quote Originally Posted by Ken Lee View Post
    Could you please summarize that thread ? I'll have to read it several times to discover the "takeaway" of what Stephen Benskin has explained. It's going over my head at the moment.
    Sure, but very, very roughly.

    It does appear very true that 18% gray is not what things are calibrated to.

    Closer to 12% but there isn't an absolute value, there is simply a standard range contained in an ISO standard.

    (For examples of people adjusting to this simply read the directions included with a Kodak gray card and you get an offset that corrects the meter reading to get the exposure setting. Ansel also complained about the K factor used by meter manufacturers.)

    The thread at the link goes through a lot of why and how the standard ended up where it is today. Changes from ASA to ISO, safety factors, placement in relation to speed point...

    The big take away I got was that believing your meter at box speed and following the directions when developing is a very reliable way to get good negatives.

    Another take away is that shooting at alternative speeds, is simply a personal placement choice. If one likes more shadow detail 1/2 box speed can get you that. This also avoids underexposure mistakes, it provides a bigger safety factor.

    A third take away, for me, is that personal film testing to get a personal EI is exactly that, personal. We don't all shoot the same way. Mid-tones and highlights are more important to me than shadow, box speed gives me plenty of shadow. That's good for me but others have different priorities.
    You can't depend on your eyes when your imagination is out of focus. ~ Mark Twain

  3. #23

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    Re: BTZS, Zone System, Everyone Else... Film Speed ?

    Quote Originally Posted by Ken Lee View Post
    True enough. But isn't it a rather unusual "coincidence" that after testing, most people arrive at the same basic adjustment ?
    I didn't.

    I'd also suggest that most people don't test and can truly do fine work using the boring old published numbers from Ilford, Kodak, Fuji...
    You can't depend on your eyes when your imagination is out of focus. ~ Mark Twain

  4. #24

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    Re: BTZS, Zone System, Everyone Else... Film Speed ?

    Dupe
    You can't depend on your eyes when your imagination is out of focus. ~ Mark Twain

  5. #25

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    Re: BTZS, Zone System, Everyone Else... Film Speed ?

    Quote Originally Posted by Ken Lee View Post
    There's nothing in the zone system that says the "real" film speed is 1/2 the box speed. The film speed is determined by testing. It might end up being 1/2 the box speed or it may not.



    I learned the Zone System from Fred Picker around 1970. Ansel had tested Tri-X + HC-110 and determined a film speed of 250. Fred did his own tests, and determined a speed of 250. I did my own tests and determined a speed of 250. It makes sense after all: we were all testing the same film and developer combination, doing the same basic agitation, with a decent thermometer, etc.
    This is my experience exactly. After reading Fred picker's book (which finally de-mystifyed the Zone system for me), I tested Tri-X with HC110 (B solution) and came up with an EI of 250.

    Recently, I tested with X-TOL 1:1 and the result was twice box speed: confounded, I tested again and got the same results; pictorial negs at the new speed look like the have been exposed correctly.

  6. #26

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    Re: BTZS, Zone System, Everyone Else... Film Speed ?

    Quote Originally Posted by Ken Lee View Post
    Could you please summarize that thread ? I'll have to read it several times to discover the "takeaway" of what Stephen Benskin has explained. It's going over my head at the moment.
    Just visit http://btzs.org/.

    Phil lays it all out.

    Using the BTZS software is also very helpful.

  7. #27
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    Re: BTZS, Zone System, Everyone Else... Film Speed ?

    Just visit http://btzs.org/....Phil lays it all out.


    In post number 18, I've already quoted verbatim from his book, listing the actual page number. In post number 1, I summarized his points. I have already laid out - twice - what he lays out.

    What he has laid out, is what I'm asking about.

  8. #28

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    Re: BTZS, Zone System, Everyone Else... Film Speed ?

    Quote Originally Posted by Ken Lee View Post
    There's nothing in the zone system that says the "real" film speed is 1/2 the box speed. The film speed is determined by testing. It might end up being 1/2 the box speed or it may not.

    True enough. But isn't it a rather unusual "coincidence" that after testing, most people arrive at the same basic adjustment ?

    I learned the Zone System from Fred Picker around 1970. Ansel had tested Tri-X + HC-110 and determined a film speed of 250. Fred did his own tests, and determined a speed of 250. I did my own tests and determined a speed of 250. It makes sense after all: we were all testing the same film and developer combination, doing the same basic agitation, with a decent thermometer, etc.
    I have no idea whether after adequate testing "most people" arrive at 1/2 the box speed or not. A lot of people use that without testing and it certainly would be a good speed to use for starters if someone doesn't want to bother with testing. And maybe "most people" end up there even after testing, I really don't know. But it wouldn't be surprising, after all how big a variation can there be from the box speed? The likely range of differences is pretty limited.

    But in standard zone system methodology there's nothing to my knowledge that says to ignore testing for film speed and just use 1/2 the box speed. Which I thought was your original question.
    Brian Ellis
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  9. #29

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    Re: BTZS, Zone System, Everyone Else... Film Speed ?

    Users of large format cameras have tended to rate their film at about 1/2 of box speed. The main reason is that there seems to be a preference among view camera users to get good detail and contrast at the very bottom of the toe in the open shadows, and the only way to do that is to increase exposure so that Zone II details falls on the straight line section of the curve. This practice was wide spread with Tri-X 320, which with most developers has a notoriously long toe.

    Some of the modern T-grain films produce by their nature a much more linear curve and can be used a box speed and still give good detail in the shadows.

    Assuming the same type of metering practice this issue is, strictly speaking, not a BTZS issue but one that relates to the characteristic curve type of films/developers.

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    Last edited by sanking; 5-Mar-2012 at 09:18.
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  10. #30

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    Re: BTZS, Zone System, Everyone Else... Film Speed ?

    Quote Originally Posted by D. Bryant View Post
    Just visit http://btzs.org/.

    Phil lays it all out.

    Using the BTZS software is also very helpful.
    That is not the same info or a summary of what the thread I linked to offers.
    Last edited by Mark Barendt; 5-Mar-2012 at 09:00. Reason: Clarity
    You can't depend on your eyes when your imagination is out of focus. ~ Mark Twain

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