Double exposure 'transparency' calculation.

Discussion in 'Exposure Discussion' started by batwister, Jun 27, 2012.

  1. batwister

    batwister Member

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    I have something in mind for a double exposure with a portrait and landscape image.

    I've tried to emulate the desired result in photoshop with digital images, by adjusting the transparency of the top layer - obviously achieving the same result on film will be quite different. Transparency in the case of Photoshop doesn't effect the dynamic range of the image like exposure would with film - the highlights being more apparent - but rather Photoshop considers the image a 'global tonality', adjusting the image in a linear fashion, shadows and highlights alike.

    Basically the landscape image, which I'd like to be only just visible over the portrait, is at 15% in Photoshop. This is as much as I'd like the image to be visible on film, the portrait of course being fully exposed.
    How exactly would I go about achieving this result on film?

    Hope that makes sense!

    Here's a test image of the kind of result I'm after:
    https://lh6.googleusercontent.com/-neJ-PtX0U-A/T-stD34f4gI/AAAAAAAAAWo/Od7dS5Uqtec/s640/blogger-image-773786277.jpg

    As you can see the blades of grass need to be a higher tonality than the dark background for the effect to work. Is this even possible without overexposing and therefore that image being most dominant? I can't get my head around it.
     
    Last edited by a moderator: Jun 27, 2012
  2. Vaughn

    Vaughn Subscriber

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    The more light that hits the film, the darker it gets. That is the main thing to remember as that is what affects how the two images will look like on top of each other. Dark areas on one image (little or no exposure) will allow the other image to dominate in those areas. Highlight areas in one image will block information in those areas from the other image.

    Her skin tones are just above middle gray, so it allows for the information from the other exposure to come thru...but not as much as in the darker background.

    Another important thing is how you are going to print it. If you are using a double exposure, two sandwiched negatives, or two seperate negatives exposed seperately onto the photo paper, the results will differ. In the last method, it will be the shadow areas of one image that will block the information from the second image.

    So how you plan on printing the image will determine how you go about making the negative(s).

    Vaughn
     
  3. jeffreyg

    jeffreyg Subscriber

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    You could also consider making two separate negatives and printing one over the other on the same sheet of paper. That way you could determine the exposure and contrast as well as any dodging or burning you may want. Jerry Uelsmann printed five or more negatives (using multiple enlargers) to make one image. If using one enlarger you will have to take the paper out after the first exposure to switch and focus the second so make some indication with a pencil on the back of the paper to place it correctly back in the easel.

    I have printed four separate images on one paper using masks. Time consuming but it worked. Lucien Clergue did many in camera double exposures on 35mm with the exposures from different locations and times. I don't know how he registered the film after rewinding but I know he does it because years ago he photographed a model in my backyard over photographs of paintings taken in museums using as I recall a Minolta 370 and no tripod.

    http://www.jeffreyglasser.com/
     
  4. batwister

    batwister Member

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    Right, so it's simply a case of determining the separation between that background and the grass - whether it's a stop or two, then expose accordingly? In this case, I would place the grass on middle grey or perhaps half a stop below, as not to obscure the face? I am talking about an in camera double exposure here.