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  1. #11
    markbarendt's Avatar
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    Quote Originally Posted by Rudeofus View Post
    Box speed may well be based on physical facts, but requires a procedure which is rarely followed in practical work. See my point above.
    So the problem is the user. I agree there.

    But those procedures are not tough.

    For example; incident meter, set camera, shoot.
    Mark Barendt, Ignacio, CO

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

  2. #12
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    Quote Originally Posted by markbarendt View Post
    So the problem is the user. I agree there.

    But those procedures are not tough.

    For example; incident meter, set camera, shoot.
    +1
    Ben

  3. #13
    markbarendt's Avatar
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    Quote Originally Posted by Rudeofus View Post
    Box speed may well be based on physical facts, but requires a procedure which is rarely followed in practical work. See my point above.
    Pas to latency, IIRC, it is real but factored in and not a significant problem in normal circumstances.

    http://www.apug.org/forums/forum37/8...-negative.html

    http://www.apug.org/forums/forum37/9...stability.html
    Mark Barendt, Ignacio, CO

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

  4. #14
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    Mark, you found it! (I had made two searches without success).

    The test by Stephen Benskin is very interesting indeed. Considering that the box ISO value already incorporates the "speed loss" due to latent image decay, one can say that if the exposed film is kept in the fridge between exposure and treatment the speed loss is basically non relevant.

    The table published by Benskin gives an index of 71 for 7 days (this is incorporated in the ISO measure) and an index of 65 after 31 days. The speed loss of the latent image (6/71) in four weeks out of the fridge is around 8% (around than 0.16 EV if I get it right, which is not guaranteed anyway ).
    Fabrizio Ruggeri fine art photography site: http://fabrizio-ruggeri.artistwebsites.com
    Stock images at Imagebroker: http://www.imagebroker.com/#/search/ib_fbr

  5. #15
    markbarendt's Avatar
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    Took me three trys.
    Mark Barendt, Ignacio, CO

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

  6. #16

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    Box speed is usually best, especially with built in light meters. These films are more tolerant to over exposure than underexposure, but the latitude of most of them is pretty great. Overexposure results in a washed out look, evident even with one stop overexposure but not obnoxious until about two stops with most films. Underexposure is a lot like underexposure with black and white - muddy with little tonal range. You will definitely notice a one stop underexposure; at two stops the negative will generally be useless. As I understand it, the speed rating system for color films is a bit different than for black and white, and it gives a speed that better reflects actual practice. Of course, your individual metering and picture taking technique may affect this; so your individual experience with a particular film may vary.

  7. #17
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    I often shoot at 1/3 to 1 stop overexposed on my color print film. A lot of it is old, and though it has been cold stored, I try to always be safe just in case it has lost speed due to its age.

  8. #18
    Derek Lofgreen's Avatar
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    I did a little text of my own with some Kodak consumer film. It's not super technical so for all of you super number, science/engineer types it may not help but if your like me and you want to SEE what it looks like when you change ISO settings on film then you can see one example on my blog.

    I always over expose C-41 film from the box speed. I do it because I like it. Some like it really over exposed and some folks not so much. It's really a personal choice more that technical for me.

    Hope it helps,
    D.
    My Photography Site www.lofgreenimages.com and My Blog

  9. #19
    RPC
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    Quote Originally Posted by benjiboy View Post
    I always work on the principal that the film manufacturers know better than I what the speed of their films are, and unless I consistently get under or overexposed results I stick to the boxed speed.
    But there is more to it than that. One's shutter speeds at various settings, apertures at various settings, meter and metering technique may not be totally reliable, giving one exposure errors when least expected. I believe that unless one has tested these well, then a half a stop to a stop of overexposure is a good idea. This will help insure preservation of shadow detail without compromising highlights as mentioned earlier, for both over- and under- exposure errors, unless the errors are very large.

  10. #20
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    Quote Originally Posted by markbarendt View Post
    Pas to latency, IIRC, it is real but factored in and not a significant problem in normal circumstances.

    http://www.apug.org/forums/forum37/8...-negative.html

    http://www.apug.org/forums/forum37/9...stability.html
    Looking at the second thread, I really wonder whether Stephen tested some film with ISO 71 or whether box speed was actually 100.

    Just asking ...
    Trying to be the best of whatever I am, even if what I am is no good.

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