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Thread: Long exposures

  1. #1

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    Long exposures

    I want to take some pretty long exposures... 6-8 hours, for a project I'd like to do. Am willing to use any B&W film, but 400TX is my preference since I use a lot of it. I have no real questions to ask, but was looking for some pointers. I took some test exposures, but the room was apparently too dark, and I didn't get sh*t. Does reciprocity failure step in at some point and just end it? I can always light the room a bit more, but I'm worried about extreme overexposure...

    Thanks in advance for helping out with such a vague request.

  2. #2
    Kevin Caulfield's Avatar
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    Reciprocity failure sure does step in, for some films once you get into the seconds and tens of seconds, and by the time you get into 6 to 8 hours, you could be looking at a correction factor of at least 4 or 5 (or maybe a lot more).

  3. #3

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    what are you shooting that requires a 6-8 hour exposure with 400iso film?

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    Murray@uptowngallery's Avatar
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    A dark room.

    No, seriously, reciprocity failure at 6-8 hours will be far beyond a factor of 4-5 for 400 Tri-X.

    I apologize if I misunderstood 400TX as Tri-X if Tmax was intended.

    Consider Kodak's reciprocity failure correction chart that only goes to 100 seconds: 1200 is the suggested corrected exposure, a factor of 12.

    For longer exposure, there is a chart on the web somewhere; try Googling the following keywords: Lunarlight, Kitathome,mkaz and mkirwan
    Murray

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    Dan Henderson's Avatar
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    If reciprocity failure is the issue, consider using Fuji Acros. It does not require reciprocity correction, (at least up to a point, which you may have exceeded.) You may also be shooting in such a dark place that there is not enough light energy present to affect the film, even at these extreme times.


    web site: Dan Henderson, Photographer.com

    blog: https://danhendersonphotographer.wordpress.com/

    I am not anti-digital. I am pro-film.

  6. #6

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    I'd be intrigued to know more about your initial experiment. I believe if you could see at all, your 400 speed film would have registered something with an open shutter for 6 hours.

    In other words, a very, very dim safe light would fog a piece of film in no time at all. It stands to reason, if I leave a piece of film on the counter all day, it would have to be pretty dark (as in totally) not to fog.

    Cheers,
    Russell
    Russell

  7. #7
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    Look in www.unblinkingeye.com for the article "LIRF is Lurking at Your F-stop" by Patrick Gainer. LIRF is Low Intensity Reciprocity Failure. The equation is simple, but logarithmic. The necessary factors are listed for 400TX, HP5+, and some other films. The factor you need for any film is the additional exposure needed to correct for reciprocity at 1 second measured exposure.

    The necessary additional exposure is lower by far for the TMax films and many other modern films than for the traditional films when you get out to the hundreds of seconds of indicated exposure.

    If the math gives you a headache, take two aspirin and call your nearest math doctor in the morning.
    Gadget Gainer

  8. #8
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    What do you mean, you didn't get sh*t? Was the neg fogged or was there no detail? No density? Too much density? I am very surprised if you got nothing. I haven't done many long exposures but what little I've done, I always got something. I don't know if I would even bother to think about reciprocity past a few hours, the derivative is totally flat out there anyway. Just open up the lens and the shutter and you have to get some density.
    "Only dead fish follow the stream"

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    Alright, so a bit more background is needed. First of all, I didn't try the experiment with Tri-X since it wasn't in the camera at the time. Used some Gekko MW100+. I wasn't too concerned if I didn't get printable pictures because I thought I'd get something. I got nothing. Nothing at all.

    I'm taking pictures of people sleeping. Long exposures over the whole night. Testing it on myself. The problem is, my bedroom is DARK. I could always add some light like I said, but I really want to capture it over 6 hours. As a result, I figure it's a bit more complicated than flipping on a lamp, since I'm really looking for a long exposure, and not "just enough" light for an exposure at all.

    I'm not particularly sold on any kind of film for this, but merely mentioned Tri-X because I generally like it and have a lot of it.

    I know the camera was working, etc., for 2 reasons. First, other shots on the roll came out fine. Second, when I got up in the middle of the night to use the little boy's room, I flipped on a light in the hallway and that portion of the frame exposed fine.

    I figured the reciprocity failure wasn't a big deal like keithwms said. Just because I'm opening up the shutter, picking an aperture at semi-random, and just going with it. I mean, how do I even measure the appropriate exposure which I would then adjust for reciprocity failure?

    Thanks for the link. Math isn't too scary. I use enough of it in the day job. Thanks for the ideas as well. I think more experimenting is in order; I was really just curious what your guys thoughts. I'm always impressed by the wealth of knowledge here - a great resource for a beginner like me.

  10. #10

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    Quote Originally Posted by jordanstarr View Post
    what are you shooting that requires a 6-8 hour exposure with 400iso film?
    Now there is a question worth its weight in gold!

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