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  1. #101
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    I know CI is important to these discussions that are highly technical in nature. But, a ZS practitioner (if he or she considers themselves strict about it) does not really consider CI or any other measurement of contrast that connects points on the curve with a straight line. It's the comparison of the entire curves of at least two films or one film with different developers that is considered most valuable. It's just a thought.

  2. #102

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    That is still the way I do it. I expose and develop the test films and plot the densities. A lot of it has to do with the fact I am very often working with SBRs > 10 stops. It is critical I know the shape of the curve from threshold to zones XIII-XIV under a variety of development methods. The thing I'm missing in my tests is always a flare factor, but I never really understood flare until I started reading Stephen's threads. I'm still not 100% on it, but I'm learning.

  3. #103
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    Michael, we should put effort into something that's not a waste of time. Are there any specific wrinkles in your understanding of flare?
    Last edited by Stephen Benskin; 02-17-2012 at 06:55 PM. Click to view previous post history.

  4. #104
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    Quote Originally Posted by Michael R 1974 View Post
    The thing I'm missing in my tests......
    Are you referring to tests for your effective EI's?

  5. #105
    Bill Burk's Avatar
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    Michael,

    How do you test for Zone XIV? I guess a camera test where you expose at f/11 for 1 second in daylight would about do it, but is that what you do?

    So you've heard the argument that a flat-tone subject is flare free. And you want to estimate how much flare your camera/lens/subject causes?

    I know it sounds simple but all I would do for a flare test is take a few regular pictures and make notes of the different meter readings in the subject*, making sure to pick a subject that can be clearly sketched and with different shadow areas and with a full subject range. If you have a coffee can painted black inside or a top-hat you can throw in, all the better.

    Then after developing that negative, just cross-check all your meter readings with what you got.

    I believe the difference is going to be due to flare. (If it isn't due to development times or exposure errors)

    *It may help to walk right up to the subject and take really close up meter readings. The reading I get underneath a car is greatly different when I spotmeter from a distance, and when I walk right up to it. Maybe note both meter readings. It might turn out your spotmeter has same/similar flare as your camera making the spotmeter reading accurate at predicting what hits the film.
    Seems to me any discrepancy between meter reading and actual result... would be flare.

  6. #106
    Bill Burk's Avatar
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    Quote Originally Posted by CPorter View Post
    I know CI is important to these discussions that are highly technical in nature. But, a ZS practitioner (if he or she considers themselves strict about it) does not really consider CI or any other measurement of contrast that connects points on the curve with a straight line. It's the comparison of the entire curves of at least two films or one film with different developers that is considered most valuable. It's just a thought.
    I agree curve families are extremely valuable.

    But I believe ZS practitioners connect points on the curve with a straight line, and I like to think as an homage to ZS, the points used to determine CI were chosen in much the same way as ZS - by relating to actual paper...

    To find Zone System N development time, you look for a curve that fits two points:

    Point 1 X = Zone I
    Point 1 Y = almost black on the print

    Point 2 X = Zone VIII
    Point 2 Y = almost white on the print

    And then to solve for other development times you change Point 2 X, for example...

    N+1 solve for Point 2 X = Zone VII
    N-1 solve for Point 2 X = Zone IX

    Applying Zone System development times for N, N+1, and N-1 is easy - develop for the times you wrote down.

    To apply Contrast Index in the darkroom you have to solve "word problems" to find development times.

  7. #107
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    Quote Originally Posted by Bill Burk View Post
    To apply Contrast Index in the darkroom you have to solve "word problems" to find development times.
    I have to disagree with this one Bill. First, not saying anything is wrong with CI, only that within the context of the ZS (yes, I'm speaking as taught in The Negative), CI is not needed to find "N", "plus", or "minus" times. It certainly can be if one chooses to employ the ZS using CI, mean Gradient, whatever, to find their times, but as it is taught from the source, it is not. I've got development times for TMX with d-76 1:1 and hc-110 1:63 and 1:119, I did not use CI to determine them, they were determined as taught and they work quite well. My comment about ZS practitioners was poorly worded, there are many ZS practitioners, but it is evident that there are those who are quite fluent with it and those, well, I'll just leave it there.

    With d-76 1:1, which is quite a straight-lined curve in my process, gamma can be easily determined, however, finding gamma, is not required to find development times.

  8. #108
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    Quote Originally Posted by Bill Burk View Post
    It may help to walk right up to the subject and take really close up meter readings. The reading I get underneath a car is greatly different when I spotmeter from a distance, and when I walk right up to it. Maybe note both meter readings. It might turn out your spotmeter has same/similar flare as your camera making the spotmeter reading accurate at predicting what hits the film.
    Seems to me any discrepancy between meter reading and actual result... would be flare.
    Metering along the lens axis from the camera position, IMO, would be most representative.........the light has to travel that distance to the film. Therefore, the meter reading should also be from that distance, IMHO.

    This is more directed at Michaels comments on his flare issues----my approach to it, not scientific, only practical:
    If I am concerned about flare being a particular problem with an exposure, I make a small exposure adjustment to the meter reading by stopping down, usually just a 1/3 to 1/2 stop to try and keep my shadow placement as true as possible. I have 1/3 stop pencil marks evenly spaced between the aperture values on my lenses, in case one is wandering, works well for me so far. I simply cannot subscribe to the idea of there always being a 1 or 1 1/3 stop of flare present just because I have a lens on my camera..........flare is certainly a consideration, it is never a consistent thing, but I believe it has been my experience that the image contrast and subject contrast can, not always, be quite close (with quality multi-coated lenses), but is never perfectly matched either.

    Flare is not a consideration when I carry out EI tesing either, I just try to compensate for it on a negative by negative basis, if at all.
    Last edited by CPorter; 02-18-2012 at 09:01 AM. Click to view previous post history.

  9. #109
    Bill Burk's Avatar
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    Quote Originally Posted by CPorter View Post
    I have to disagree with this one Bill. First, not saying anything is wrong with CI, only that within the context of the ZS (yes, I'm speaking as taught in The Negative), CI is not needed to find "N", "plus", or "minus" times. It certainly can be if one chooses to employ the ZS using CI, mean Gradient, whatever, to find their times, but as it is taught from the source, it is not. I've got development times for TMX with d-76 1:1 and hc-110 1:63 and 1:119, I did not use CI to determine them, they were determined as taught and they work quite well. My comment about ZS practitioners was poorly worded, there are many ZS practitioners, but it is evident that there are those who are quite fluent with it and those, well, I'll just leave it there.

    With d-76 1:1, which is quite a straight-lined curve in my process, gamma can be easily determined, however, finding gamma, is not required to find development times.
    I think you read me wrong because I think we are in agreement.

    You are absolutely right, Zone System is self-contained and it gives you development times that you can use right away. To use ZS you don't need to know or be aware of CI (or similar Gamma which uses less practical points the paper can't use). The Zone System works, and I enjoy reading and writing about it in its purest form, its history, and the ideas that have followed. We live in a wonderful time when we can go back in time and use historic ideas, that still work.

    Contrast Index is part of a different system, the two different systems use different vocabularies and procedure steps but seek a similar goal using similar information... to find film development time given shooting conditions. To use CI, you don't need to know ZS.

    After you find your times, you don't have to do any more math... but I have to do "word problems".

    Word problems like my kids get in math...

    Bill took a picture in bright sun and spotmetered a shadow and placed it on Zone II. He spotmetered an important highlight and found it was falling at Zone VII, so he made a note to develop N+1. He uses NDR 1.00 as a target to fit his paper. What is the development time in D-76 1:1?

    Bill has a lot of math to do before he gets his answer:
    1. N+1 implies Zone I through Zone VII, subject brightness range 6 stops.
    2. 6 x 0.3 = 1.8
    3. Subtract 0.4 for flare
    4. 1.00 divided by 1.4 = 0.71
    5. From previously-prepared lookup chart for Time/CI for TMY2 in D-76 1:1, 0.71 = 15 minutes

    Chuck took a similar picture, and also made a note to develop N+1. He uses NDR 1.20 as a target to fit his paper. What is his development time in D-76 1:1?

    Chuck gets his answer at a glance:
    1. Look at N+1 on chart and develop for that time. Maybe 18 minutes?

    Why do we get different times? Because we use different paper. What happens if Chuck wants to use Bill's paper? Chuck has some testing to do but he knows the steps and it's fun to do. What happens if Bill wants to use Chuck's paper? He plugs the number 1.20 in step 4.

  10. #110
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    Quote Originally Posted by CPorter View Post
    Metering along the lens axis from the camera position, IMO, would be most representative.........the light has to travel that distance to the film. Therefore, the meter reading should also be from that distance, IMHO..
    I agree. When you meter at the camera, it is like you already factored in flare.



 

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