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Thread: Need help calculating double long exposure

  1. #1

    Join Date
    Nov 2010
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    Need help calculating double long exposure

    I've decided to make a series of photographs with portraits in front of distorted buildings. When I distort them with movements, I get very shallow DOF, so I need to use f64 (tried f32 - not sharp enough). My flashes aren't powerful enough to correctly expose the person at that aperture, so I am thinking about focusing to the person, take one exposure with flashes at about f8-f11, and then close it down to f64 and expose for the background.

    The problem is that I am new to the night/long exposure photography. I've made a couple of test shots. Here's the ruined one:


    The flashes worked twice, since it was a long exposure. I metered the scene it was about 12min at f32. I didn't make any compensations for the reciprocity, and it came out overexposed. The film is cross-processed, maybe that might effect somehow.

    Anyway any tips on exposre or which parts to meter? I am shooting expired ektachrome 100


    Thanks
    www.photoshoo.com

  2. #2
    Downstairs
    Join Date
    Feb 2008
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    Italy
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    1,449

    Re: Need help calculating double long exposure

    Quote Originally Posted by shOo View Post
    ... I am shooting expired ektachrome 100...
    Daylight Ektachrome does not take at all kindly to long exposures. If you can find it, you should use (expired) Ektachrome T, for tungsten light, with an orange conversion filter.
    With T film you can do very long exposures without colour shift.
    Usually, people do a dusk exposure for contents then a night exposure for lights. Your girl will always be burned-through by the dusk-exposure sky, unless she can hold still for a minute or so to act as a mask.
    To calculate exposure, you might read the dusk sky and shoot that reading, multiplied by the reciprocity table calculation that comes with the film. The lights exposure needs about twice as much as the dusk reading, plus allowance for reciprocity.
    Someone correct me if they have better advice.

  3. #3

    Join Date
    Oct 2009
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    San Mateo, California
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    Re: Need help calculating double long exposure

    Quote Originally Posted by shOo View Post
    I've decided to make a series of photographs with portraits in front of distorted buildings. When I distort them with movements, I get very shallow DOF, so I need to use f64 (tried f32 - not sharp enough). My flashes aren't powerful enough to correctly expose the person at that aperture, so I am thinking about focusing to the person, take one exposure with flashes at about f8-f11, and then close it down to f64 and expose for the background.


    The flashes worked twice, since it was a long exposure. I metered the scene it was about 12min at f32. I didn't make any compensations for the reciprocity, and it came out overexposed. The film is cross-processed, maybe that might effect somehow.

    Anyway any tips on exposre or which parts to meter? I am shooting expired ektachrome 100


    Thanks
    It looks like it is exposed OK in the shadows. The cross-processing seems to reduce the film range so the sky blows out.

    You will probably have a lot more testing before you figure out reciprocity for cross-processed expired film. I don't think there are tables available for that.

    As for the person in the foreground, you might want to make sure they have a darker area behind them so they will show up or make sure they stay in the same place.

    Or you could make two exposures and blend them in in photoshop. That way you can have both person and building in focus :-)

  4. #4

    Join Date
    Nov 2010
    Posts
    23

    Re: Need help calculating double long exposure

    Thanks, well I understand about the brighter sky. But that building has some green lights around the windows, so I am thinking about shooting it at night. That way the sky shouldn't be brighter than the model's face
    www.photoshoo.com

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