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Thread: Pre Exposure

  1. #1

    Pre Exposure

    I will be doing a lot of traveling for the next two months and room and weight w ill be an issue. I am taking the minimum amount of 4x5 stuff. One of the items I am considering leaving behind is my double walled plexiglass pre exposure dev ice. Should I be able to accomplish the same result by doing the pre exposure w hen I get home ? Although technically that would make it a post exposure. Any reason why the pre exposure can't be done after the fact? Thanks.

  2. #2

    Join Date
    Mar 1999
    Posts
    769

    Pre Exposure

    Will work fine. As long as you keep track of what needs post exposure. Cheers. DJ

  3. #3

    Join Date
    Sep 1998
    Location
    Oregon now (formerly Austria)
    Posts
    3,397

    Pre Exposure

    Paul, What a great idea! It's things like this, which never occur to me for some reason, that make this forum so worthwhile! Not only can you wait till you get home to make your "post-exposure", you can expose a few sheets in the field, develop one after post-exposure and adjust the post-exposure for the others a bit to fine tune if necessary, all in the comfort of your own living room! Regards, ;^D)

  4. #4

    Pre Exposure

    Paul: I would think you might want to do some tests first to see if you get the effect you are looking for. Pre-exposure helps mask some of the contrast in a scene, but it also helps to bring the exposure level of the shadows past the threshhold level of the film. Post exposure may work fine, I've never tried it, but I would see if it works o.k. before risking a lot of work and negatives. I would certainly test for the shadow areas. I'm not trying to throw a wet blanket on your idea. Hope it works out great for you. Let us know the results.

    Regards,

  5. #5

    Pre Exposure

    I hate to put a damper on things, but I don't think you'll get the same effect.Latent image regression will most likely knock out the very low levels of exposure that you're trying to capture, before you can give them the post exposure.You could always carry a few sheets of pre-flashed film with you, but again, you'd have to give more than your usual pre-exposure to accomodate the regression between pre-exposure and exposure proper.

    Do you regularly take pictures of fireflies by starlight BTW? Why not just give more exposure, and pull the developer a bit? Or use a less contrasty film?

  6. #6

    Pre Exposure

    I use pre-exposure all of the time. Most contrast situations I find in my scenes require it. I used to think that pre-exposure worked best and post exposure was for other applications. Having run some pretty precise tests I was proved wrong. Post exposure is the same as pre-exposure. And now I can really tailor my post exposure precisely. Don't hesitate to use it. But keep precise notes of each exposure so when you get back it will be easy on you. But it is such a valuable tool, don't hesitate to use it's advantages help those shadows and the contrast range within the scene. James

  7. #7

    Join Date
    May 2006
    Location
    Arizona
    Posts
    377

    Pre Exposure

    This may sound dumb (I haven't tried pre or post exposure yet) but can't you mount a plexiglass piece into a filter ring and have it occupy much less space? Doesn't anyone market this? I can understand the advantages of a dual-walled device to ensure eveness of exposure. What plexiglass can be recommended for this, are there neutrality problems? Last question: what lighttight boxes are on the market for unloading filmholders in the field?

  8. #8

    Join Date
    Apr 2000
    Location
    Calgary
    Posts
    338

    Pre Exposure

    Wayne,

    you need a Wallace Expo Disc, from (you guessed it ) Wallace Photo Products. Should do the job. He has a web site. You can also use it to check your light meter, or to expose sheets for Zone I and Zone VIII to throw in with a batch of exposed film occasionnally-to use as a rough Exp/dev control. If you stick one on your enlarging lens you can pre expose (flash) your printing paper, in the field use it for pre exposure of film.

    Regards.

  9. #9

    Pre Exposure

    James M.: Glad to see someone ran some test on a process I'd never even thought of. It sounds like it could be a really good tool. All of us come back from shoots where we wished we had had a few pre- exposed sheets. Could you post a few more details, such as how much post-exposure you give and how do you judge how much to give?

    Thanks,

  10. #10

    Join Date
    Nov 1998
    Posts
    93

    Pre Exposure

    Doug, I have used this approach for the last 10 years, ever since John Sexton helped to save an exposure the he said would other wise not turn out. I was photographing in the same location as his Grotto Interior photograph, which is a cave with an opening at the top. The problem was plenty of light at the top of the image and very little light in the shadows. I was using T-Max 400 and gave an exposure of 5 minutes at f/22. John walked in during the exposure and asked the details of the exposure that I was making and he suggested that it would not be enough. When we got back to where the workshop was being held we added a Zone II exposure to the exposed film and that image prints with a full range of detail. Generally, I add a Zone II exposure when ever using this technique. A Zone I exposure would probably also be acceptable but even at Zone II I find it easy to print threw even if it is too much. Give it a try.

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