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Thread: Zone Placement

  1. #41
    Bill Burk's Avatar
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    Quote Originally Posted by Stephen Benskin View Post
    Personally, I don't like using Zone terminology as a general rule. I kind of had to in this thread. Yuck.
    I know you prefer reasoned sensitometry to Zone System and work ceaselessly to encourage thoughtful use of it to those who want to use the Zone System.

    Quote Originally Posted by Stephen Benskin View Post
    As the CI chart is sort of connected with the concepts of this thread, I have a challenge to present. Anyone know how the CI values were produced? What were the factors involved? Bonus points for an analysis of any strengths or weaknesses of the model.

    I can give a strength of ***this model*** that I bet you never thought of. I graph my curves on paper. And I use a CI transparency overlay to read the graphs.

    With more sensitive film, the sensitometer tends to "overexpose" the film being tested when using a 21-step test wedge. Any faster than 400 and I won't have a toe on my graph and I may not even have an 0.1 density reading to gauge speed by.

    But my CI index will fit nicely on the graph. So I will know my CI.

    ***Thought you were talking about CI 'per-se'.

    Now that I've printed the chart I know you are talking about something else.

    This is same as Zone system except not using Zones at all. Not using N+ or N- either. Just tells you what to develop to if you want to get a print matched to the negative based on your meter reading. Nice. I was going to extrapolate something like this anyway since it is easy for me to develop to a CI.
    Last edited by Bill Burk; 09-08-2011 at 11:06 PM. Click to view previous post history.

  2. #42
    Stephen Benskin's Avatar
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    Okay Bill, chose a value on the chart. How did they arrive at that number?

  3. #43
    Bill Burk's Avatar
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    When I take a paper with LER 0.9 (Galerie 3 in my hands) and follow the 0.50 CI curve on paper from 0 to 7 stops (Zone 0 to Zone VII at N), I arrive at my LER 0.9 in 7 subject light meter stops.

    But on the chart, that isn't where 0.50 CI is prescribed, it's 2/3 stop to the right at 7 2/3 subject light meter stops.

    0.56 is the prescribed CI.

    Oddly (or not - depends how you see things), <N> that I wrote on my graph, is on the 0.56 CI curve where it crosses Zone VII. I put that <N> there after working with you to incorporate flare.

  4. #44
    Stephen Benskin's Avatar
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    Flare, eh? And...

    Check out the CIs from the processing tables in this Kodak Xtol data sheet. They start on page 6. What does it have as Normal? Where does that fit into the CI chart? Don't try and figure out the pluses and minuses they have for Xtol just yet. It will just confuse you as they don't match up with the Kodak CI chart. Bonus if anyone can figure that one out.

    I hope you see where I'm going with this. This is not trick. It's like I said earlier, the key is in the interpretation of the data, and a large part of that is having a good grasp of certain principles and asking the right questions. Hint: How is CI calculated?

    I'm tempted to start a new thread with this except that it also fits in well with the Zone System / Tone Reproduction negative density range question.
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    Last edited by Stephen Benskin; 09-09-2011 at 05:30 AM. Click to view previous post history.

  5. #45
    markbarendt's Avatar
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    Okay

    So using the method for determining CI found in Kodak's Sensitometry Workbook the curve used in the examples has a CI of 0.58. Close as I can tell.

    The placement of the zones can be determined by the paper's range, if the papers printable range is 1.05 then B should print the zones as expected and A would end up clipping.

    Am I missing something with regard to the paper's characteristics?
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  6. #46

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    I'm way behind the curve (pardon the pun) on this, as I must admit I've never used CIs per se in my own testing. I just test and plot. What I could never understand about CI is it seems to just be an average slope, some kind of line of best fit, or the slope of a straight line from some arbitrary min density to some arbitrary max density. Characteristic curves are not straight lines. Unless I'm just not understanding CI.

    Sorry for being a dummy on this. I've never looked at the math in CI so I'm a little ignorant here.

  7. #47
    markbarendt's Avatar
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    Yes CI is a measure of the slope.
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  8. #48

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    Quote Originally Posted by markbarendt View Post
    Yes CI is a measure of the slope.
    Right but there are other ways of looking at slopes, like average gradient for example. I'm just not keen on slopes when even straight line films have toes and shoulders, in addition to kinks.

  9. #49
    markbarendt's Avatar
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    That's why I said "a" and not "the".
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  10. #50
    Stephen Benskin's Avatar
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    Looks like a new thread on CI and average gradients would be a good idea. The use of the curve gradient is an important element in the explanation of the two curve examples, but a detailed discussion about gradient methods will just make this thread more convoluted. Anyone want to start up the new thread?



 

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