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Thread: Zone Placement

  1. #141
    Stephen Benskin's Avatar
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    Bill, quick and dirty and in a word - flare.
    Attached Thumbnails Attached Thumbnails Bills Curve.jpg  

  2. #142
    Stephen Benskin's Avatar
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    Updated. I hope this is a cleaner example. I used one of my TMY 0.58 curves which matches up closely with Bill's curve.

    This example fits in nicely with the discrepancy in the Zone System negative density range question that started this thread.
    Attached Thumbnails Attached Thumbnails TMY flare and no flare comparison.jpg  

  3. #143
    Stephen Benskin's Avatar
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    Are you thinking that because the shadow falls further to the left without flare, it means it is faster. If that is the case, then you are confusing how much exposure it takes to produce a certain density with where the exposure falls. When comparing two films, one film produces 0.10 density with X exposure. The other film produces 0.10 density with 1/2 X exposure. As the second film produced the same density with 1/2 the exposure, the film is twice as fast.

    If we are talking about shadow placement, then that's just about where the exposure falls. 1/2 less exposure is just 1/2 less exposure, and it falls .30 log-H units further to the left on the curve. With flare, you have the 1/2X exposure plus a 1/2X amount of exposure coming from flare creating a shadow exposure of not 1/2X but a shadow of X exposure. This moves the effective exposure of the shadow 0.30 log-H units to the right on the curve.

    You can also think of flare as reducing the log-H range from the metered exposure to the shadow. Instead of having 4 1/3 stops below the metered exposure, there are only 3 1/3 stops. The illuminance range is shorter and the shadows don't reach as far down the curve.
    Attached Thumbnails Attached Thumbnails Exposure Values.jpg  
    Last edited by Stephen Benskin; 09-18-2011 at 09:50 AM. Click to view previous post history.

  4. #144
    Bill Burk's Avatar
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    Quote Originally Posted by Stephen Benskin View Post
    Bill, quick and dirty and in a word - flare.
    Thanks Stephen these placements are starting to make some sense.

    If my guess is right, quick and dirty accounting for flare - set EI on meter to half box speed.

  5. #145
    Stephen Benskin's Avatar
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    I added a few things to the last example. I don't know if helps or not.
    Attached Thumbnails Attached Thumbnails Exposure Values.jpg  
    Last edited by Stephen Benskin; 09-18-2011 at 01:22 PM. Click to view previous post history.

  6. #146
    Bill Burk's Avatar
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    It helps, so for one stop of flare you add .0034 to each corresponding value of H.

    Because the scale is logarithmic, once you go up a stop or so, the added exposure becomes negligible.

  7. #147

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    Just curious, I like show n tells. I've been watching this thread since the begining n getting a real education but...

    How about scannning negs or prints n show us what the differences you found in your experiments n how all this correlates in real life compared to the graphs n charts?

    .
    Anyone can make a Digital print, but only a photographer can make a photograph.

  8. #148
    Stephen Benskin's Avatar
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    Bill, that's right, although the 0.0034 is for 125 speed film. Flare factors are calculated in the shadow. A one stop flare factor is double the exposure of the shadow exposure. That value is then added to every point along the exposure range. By the time it hits the metered exposure point it only adds up to an extra 3%. i like to use a no flare curve in Quadrant 1 as a reference. You can see for average flare, the two curves practically merge after the mid-point.

    Are you beginning to see what I'm saying about the importance of incorporating the influence of flare into a no flare test when interpreting the data? What's really helped me to understand it is separating camera exposure from sensitometric exposure with the film curve and giving it a curve of its own with the camera image/flare curve.

  9. #149
    Bill Burk's Avatar
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    Hi paul ron,

    I'll post pictures in the galleries when I get them printed. I don't have (or want) a 4x5 scanner. Basically, it was opening day of soccer season. The teams paraded by with the coaches holding their banners. It was midday, sunny. All shots are f/8 at 1/300. I spotmetered the black shorts and the kids faces.

    Whenever I checked the shorts and faces, I always got the same reading on the meter, so the lighting was stable. But because the scenery was dynamic, it is fair to ask... did my Zone placement move on me? (Maybe in reality at the moment of the shot, the faces were actually Zone V). I'm wondering that myself as some highlighted cheeks do measure over 1.00

  10. #150
    Stephen Benskin's Avatar
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    Most people are familiar with the story behind Ansel Adam's Moonrise Over Hernandez. It is arguably considered his best work. It was very underexposed. The beautiful prints he was able to create are a more a testament to his skill as a printer and his eye as an artist than to his exposure technique.



 

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