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  1. #11
    MattKing's Avatar
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    The only possible problem with mixing long and short exposures is that very long exposures may involve unusual contrast ratios that you would otherwise want to compensate for by adjusting your development.

    If that isn't the case, go right ahead.

    Matt

  2. #12

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    Thanks, Matt. Could give me an example so that I know what to consider?

  3. #13

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    Yes, but . . .any metering error (I don't know if error is the right word) will be amplified by orders of magnitude. These reciprocity curves are great, if your metering is spot-on. At normal shutter speeds, a quarter-stop slow on this one and a quarter-stop fast on that one is no big deal. But when you go several stops out on the published curve . . .extrapolating five stops out turns a 1/4 stop error into an 8 stop error. Some of these things will not be like the others.

  4. #14
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    Quote Originally Posted by Brandon D. View Post
    Thanks, Matt. Could give me an example so that I know what to consider?
    As an example, if you are shooting something like a night scene illuminated by a street lamp, the contrast may be quite harsh. If you try to compensate for that by "pulling" your development, you will reduce the contrast for all frames on the film, and that reduced contrast may not work well for those other frames.

    It isn't really a problem with the longer exposures, but rather a problem with the type of lighting conditions that often lead to the need to do longer exposures in the first place.

    Matt

  5. #15
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    Quote Originally Posted by MattKing View Post
    The only possible problem with mixing long and short exposures is that very long exposures may involve unusual contrast ratios that you would otherwise want to compensate for by adjusting your development.

    If that isn't the case, go right ahead.

    Matt
    Howard Bond, in the article from which Gainer derived his equations, found that there was no increase in contrast with Delta 100 with exposures adjusted from a base exposure of up to 240 seconds. So there's no need to worry about this problem with Delta 100.

    Quote Originally Posted by Howard Bond
    In the past, films typically yielded increased density ranges with long exposures. The extra exposure that rendered Zone III as planned was less needed in the high zones, so they were elevated, increasing the density ranges.This situation is now much improved. At 240 seconds indicated, TMax 400 and 100 Delta showed no elevation of Zone VIII.
    Lee

  6. #16
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    Lee:

    Thanks for your post. If I understand it correctly, you (and Howard Bond) are referring to the behaviour of the film when exposed for longer times. My observations were related more to the lighting conditions one often encounters when longer exposures are required.

    Matt

  7. #17
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    Quote Originally Posted by MattKing View Post
    Lee:

    Thanks for your post. If I understand it correctly, you (and Howard Bond) are referring to the behaviour of the film when exposed for longer times. My observations were related more to the lighting conditions one often encounters when longer exposures are required.

    Matt
    I was editing the Bond quote (from a messy multi-column .pdf "cut") when your post #14 to this thread came in, which makes your meaning clearer. Yes, my post is in reference to the contrast increase in the film caused by longer exposures, which isn't present in many modern films, including Delta 100.

    I'm not referring to the greater dynamic range lighting conditions found in many low light settings that you mention.

    Lee

  8. #18

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    Thanks, everyone. To tell you the truth, the long exposures I'll be shooting probably won't be shot in contrasty lighting, so I should be fine on that aspect. Stuff like this is good to know; I'd just hate to waste frames or delay on developing a roll simply due to exposure [time] variations from frame to frame. I think I should be fine, but I'll test a few rolls before I try this for real.

  9. #19
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    Search www.unblinkingeye.com for my article "LIRF is Lurking at Your f-stop". LIRF stands for "Low Intensity Reciprocity Failure." There you will see what the logarithmic curves should look like. The straight line results when one plots the amount of exposure time to be added to the time measured with the ordinary exposure meter against the measured time on log-log graph paper, or the log of one against the log of the other other on ordinary graph paper.
    Gadget Gainer

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