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  1. #11
    JBrunner's Avatar
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    Reciprocity for Delta 100- http://www.ilfordphoto.com/products/...essional+Films

    Fact sheet>second page>reciprocity for 15s exposure is about 50s

    Depending on your developer you may need more. You could go up to about two minutes without really hurting yourself.

  2. #12

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    Quote Originally Posted by JBrunner View Post
    Reciprocity for Delta 100- http://www.ilfordphoto.com/products/...essional+Films

    Fact sheet>second page>reciprocity for 15s exposure is about 50s

    Depending on your developer you may need more. You could go up to about two minutes without really hurting yourself.
    Crazy, so when exposures get up to a considerable length, time doesn`t make as big of a difference as when it`s in fractions of a second for a normal shot.

    I`m also using D76 for developing.

  3. #13
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    Reciprocity failure(borrowed from wikipedia)

    At very low light levels, film is less responsive. Light can be considered to be a stream of discrete photons, and a light-sensitive emulsion is composed of discrete light-sensitive grains, usually silver halide crystals. Each grain must absorb a certain number of photons in order for the light-driven reaction to occur and the latent image to form. In particular, if the surface of the silver halide crystal has a cluster of approximately four or more reduced silver atoms, resulting from absorption of a sufficient number of photons (usually a few dozen photons are required), it is rendered developable. At low light levels, i.e. few photons per unit time, photons impinge upon each grain relatively infrequently; if the four photons required arrive over a long enough interval, the partial change due to the first one or two is not stable enough to survive before enough photons arrive to make a permanent latent image center.
    Last edited by dehk; 10-12-2010 at 01:06 AM. Click to view previous post history.
    - Derek
    [ Insert meaningless camera listing here ]

  4. #14
    JBrunner's Avatar
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    Quote Originally Posted by Treymac View Post
    Crazy, so when exposures get up to a considerable length, time doesn`t make as big of a difference as when it`s in fractions of a second for a normal shot.

    I`m also using D76 for developing.
    Yeah, that's pretty much it, two minutes is only about a stop more exposure, or maybe less, depending on subject contrast and developing. You may also experience an expansion effect because when reciprocity kicks in different tones don't receive the same exposure as they would if the film was acting normally because density builds on the negative at different rates according to the local reciprocity effect, and this happens even if the emulsion isn't one that likes to expand when one is trying to achieve expansion using conventional methods. Charts are basically serving suggestions, and can be right on or wildly inaccurate depending on who what when where and how. In other words results may vary. It's important to be consistent in methodology and keep good records of what you did, so you can adjust or duplicate.
    Last edited by JBrunner; 10-11-2010 at 10:37 PM. Click to view previous post history.

  5. #15

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    I didn`t have enough time to do a lot of research into my project, so I`m glad my tripod broke today before I really got into taking many photo`s. I did take one with the welders glass though, so I`m looking forward to how it turns out.

    Thanks guys, sounds like I won`t have to be bracketing too much now.

  6. #16
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    Quote Originally Posted by Treymac View Post
    I didn`t have enough time to do a lot of research into my project, so I`m glad my tripod broke today before I really got into taking many photo`s. I did take one with the welders glass though, so I`m looking forward to how it turns out.

    Thanks guys, sounds like I won`t have to be bracketing too much now.
    Make sure you show me the photo taken with the welder's glass, I do have 2 masks sitting out in my shed also!!
    - Derek
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  7. #17

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    Just a niggle: when the aim is to teach about film's behaviour at long exposures (and quote Wikipedia), let's call it by its proper name, i.e. "reciprocity failure".
    "Reciprocity" of time and intensity is what we enjoy at 'normal' shutterspeeds.

  8. #18
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    Quote Originally Posted by Q.G. View Post
    Just a niggle: when the aim is to teach about film's behaviour at long exposures (and quote Wikipedia), let's call it by its proper name, i.e. "reciprocity failure".
    "Reciprocity" of time and intensity is what we enjoy at 'normal' shutterspeeds.
    Very true and correct, and a good catch. I think maybe many just say "reciprocity" when speaking of reciprocity failure because reciprocity doesn't actually concern us very much when it's working correctly.

  9. #19
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    Treymac: Meaning no disrespect, from reading your posts I think you need to learn the basics of photography, including exposure. I recommend you buy a good, beginning photography book. "Photography" by London and Upton comes to mind, but there are others. If you study one of these texts, things like reciprocity (and reciprocity failure) will make sense to you and at some point will become second nature. If you are short of funds I am quite sure that you can buy a used one from Amazon or some such place for a reasonable price.


    web site: Dan Henderson, Photographer.com

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

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

  10. #20

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    Hey guys. Ok, so I took my photo's yesterday, and developed today. The welders glass didn't turn out because I didn't give it enough exposure time. But the rest that I just used ND filters on did come out nicely. I figured reciprocity into my timing, which actually is pretty sweet because it gives me a lot more time to keep the shutter open. Unfortunately I ran into some problems with the negs though. One was from developing them, I had streaks from the carriers that look pretty awful. It's pretty disappointing. There was also another problem, and this I think came from one of the filters. There are some squiggly artifacts that show up, mostly in constant light areas like sky and water, and since that's the majority of my photo's, it's kind of really disappointing. But I did get 3 out of 10 that I think I can work with. It's going to require major cropping and the actual photo that I took is going to be lost, but at least I will have something. Good thing it's large format.

    So I'm also planning on going out again, probably next Tuesday to get some more photos. But I'm going to be using medium format 645 just because it's so much quicker to get around. And using iso 25 speed film, either Rollei Ortho 25 or Rollei Pan. At least with 25 speed film, I won't need to use as many filters, which will improve image quality as well. I love using large format but it wasn't a lot of fun packing the camera, tripod, and the rest of the equipment all over the city. I feel a little defeated, but at least my pictures did work. So my project is going to be a mix of large and medium formats.

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