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Thread: Double exposure question

  1. #1

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    Double exposure question

    What's the best way to calculate exposure for a double exposure, so as to not overexpose the film with the camera set a say F22 for the first shot and F 5.6 for the second? Double exposure is something new to me and could use a little help.

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    Re: Double exposure question

    Sorry, I wasn't paying attention to where I was posting.This should be in the Style & Technique board.

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    Vaughn's Avatar
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    Re: Double exposure question

    Generally, I would keep both exposures the same (assumimg the light was the same) -- basically photograph each scene at its normal exposure. That way, light objects will be exposed correctly when superimposed over a dark area. Two light equally bright areas will only be over-exposed by one stop.

    But it depends if you want one of the scenes to dominate over the other, etc.

    Vaughn

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    Re: Double exposure question

    Quote Originally Posted by sfjphotography View Post
    What's the best way to calculate exposure for a double exposure, so as to not overexpose the film with the camera set a say F22 for the first shot and F 5.6 for the second? Double exposure is something new to me and could use a little help.
    Here's the way I do it when I'm trying to do it intentionally. (Seems to happen unintentionally every once in a while on its own.) If your correct exposure is 1 sec at
    f22, the each exposure would be 1/2 at f22. (1/2 plus 1/2 = 1 sec.) If you want to change the second exposure to f5.6 then the exposure would be 1/30 at F5.6 if I did my math correctly. Jim

  5. #5
    runs a monkey grinder Steve M Hostetter's Avatar
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    Re: Double exposure question

    first maybe we should know what effects your trying to accomplish

  6. #6

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    Re: Double exposure question

    It depends on what sort of double exposure you're planning. If you do a Google All Words search using the words "multiple" "exposure" and "photography" you'll find a lot of information for various types of double exposures.
    Brian Ellis
    Before you criticize someone, walk a mile in their shoes. That way when you do criticize them you'll be
    a mile away and you'll have their shoes.

  7. #7

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    Re: Double exposure question

    Quote Originally Posted by sfjphotography View Post
    What's the best way to calculate exposure for a double exposure, so as to not overexpose the film with the camera set a say F22 for the first shot and F 5.6 for the second? Double exposure is something new to me and could use a little help.
    The correct way of doing this is to determine the proportion that each exposure adds to the total combined and determined proper exposure. The oft expressed rule is if two exposures of equal luminance are to comprise a single finished exposure than each exposure would be 1/2 of the exposure for each as taken as a single exposure.

    When you get into differing luminance situations than the proportion must be determined. For instance if you want to expose two exposures (with differing light conditions) with the same aperture than the shutter speeds would need to be adjusted to arrive at the proper proportional exposure of each. You always want to end at a value of one. Four exposures would (if of equal luminance) be 1/4 of the single exposure.

  8. #8
    Don Nelson
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    Re: Double exposure question

    Quote Originally Posted by sfjphotography View Post
    What's the best way to calculate exposure for a double exposure, so as to not overexpose the film with the camera set a say F22 for the first shot and F 5.6 for the second? Double exposure is something new to me and could use a little help.

    You haven't told us whether the second exposure was same scene (maybe with something changed, like moving a person to create a "ghost") or whether you were superimposing a second image on top (like pasting in a moon in a landscape where none was before).

    If the former, and you change the lens aperature -- the depth of field will change. This superimposes (possibly one in front and one in rear... if not focused near infinity) a region where the focus is sharp with another exposure where the focus is not sharp. Perhaps this is an effect you are looking for? If not, then change only the duration of the exposure while using the same lens aperature.

    Others have already explained multiple exposures so I won't repeat that here.

  9. #9

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    Re: Double exposure question

    Depends entirely on what you are doing. If your shadows from one are going on the highlights of the other and vise versa, nothing will get overexposed since no area gets two highlights put on it. If on the other hand, you are putting all highlights on the same place, you may want to back down a stop of exposure and/ or back down your development to keep highlights from blowing out.

    Marking up your ground glass helps a lot to sort out those exposure issues. Best yet, shoot with two cameras and use a sheet of mylar and mark it with both scenes. Then you'll know exactly what goes where. The highlights are the real issue since they'll create the blown out neg. Remember that two zone 5s combine to a zone six (not a 10!)and so on.

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    Resident Heretic Bruce Watson's Avatar
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    Re: Double exposure question

    Quote Originally Posted by Vaughn View Post
    Generally, I would keep both exposures the same (assumimg the light was the same) -- basically photograph each scene at its normal exposure. That way, light objects will be exposed correctly when superimposed over a dark area. Two light equally bright areas will only be over-exposed by one stop.

    But it depends if you want one of the scenes to dominate over the other, etc.

    Vaughn
    What Vaughn says.

    Bruce Watson

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