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  1. #11

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    I'm a little confused about the hour exposure in daylight. Couldn't you get rid of 2 stops of trouble by limiting it to 15 minutes, or lose another couple of stops by going down to a few minutes? Nighttime ultra-long exposures make some sense because of various sources of light that might move or take that long to make an image. But after a couple of minutes of daylight-lit stuff moving around, it's all the same at longer exposures... or am I missing something? (I've seen that guy, whose name escapes me, that takes those year-long exposures, but that's another thing entirely.)

    Duncan

  2. #12

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    Quote Originally Posted by frobozz View Post
    I'm a little confused about the hour exposure in daylight. Couldn't you get rid of 2 stops of trouble by limiting it to 15 minutes, or lose another couple of stops by going down to a few minutes? Nighttime ultra-long exposures make some sense because of various sources of light that might move or take that long to make an image. But after a couple of minutes of daylight-lit stuff moving around, it's all the same at longer exposures... or am I missing something? (I've seen that guy, whose name escapes me, that takes those year-long exposures, but that's another thing entirely.)

    Duncan



    If I'm being honest with you, it's mostly artschool bs but I think the main idea is that by stretching the exposure as long as possible I'm able to change the role that time plays in a photograph (antithesis to kodak moment, etc.). It becomes a photograph of time or maybe a photograph without time?

    Who knows, it's kind of a ploy to get my homework to be 'go read a good book for an hour' although I think it has a bit more conceptual merit than that.

  3. #13

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    Quote Originally Posted by Athiril View Post
    I've crossed polarisers before... on my digital SLR.. the histogram had a very thin range, and the range of colours were very thin as well, and very strange.

    I've pulled colour neg 14 stops before, reciprocity occurs when a certain light level is hitting the film, less % is absorbed to form the image, afaik it doesnt drop absorbing all wavelengths evenly, hence colour shift.

    A strong pull would avoid this. Sounds like for 160S, you want 18 or 19 stops of reduction or pulling.

    You'd need to use a first developer, or very dilute C41/colour dev to develop with such a pull.

    Rodinal 1+100, 1 hour, 20c stand is good for box speed as a first dev for colour negs, so I'd suggest, maybe 1+100, 9min with agitation perhaps.. would need a test.

    After that you may fix, bleach, then colour develop (C41 or E6 CD), bleach, fix.


    Otherwise, at +18 stops of exposure.. I imagine the image might even be 'burned' onto the film already, so you could possibly fix, bleach, then colour develop, bleach fix.


    May sound like odd suggestions, but seeing as you want to do something odd... Actually I might give this a test tomorrow!






    Yeah I think I've heard that the color shifts are because the separate color layers don't fail at the same rate.

    In any case, I'm not really talking about overexposing so much as I am talking about getting a proper exposure at around an hour.



    And I'm not sure I made myself clear, I already have a filter that I am experimenting with.

  4. #14
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    We can see you have a filter, but the reason people are suggesting a pull is to avoid the reciprocity problems. Reciprocity failure (RF) occurs because it takes multiple photons in a short period of time hitting the same silver-salt molecule to activate it. If it gets just one, it will revert back to its inactivated state after a little while. So with a high photon flux you get reliable activation/exposure, but with a very low flux, a good proportion of the few photons that do make it to the film will be wasted because they only partially activate a molecule, which then reverts.

    By overexposing and reducing development, you can reduce the effective sensitivity of your process (give it a longer yet correct exposure - for that level of development), which is what you want. If you achieved the same thing only by filtering, you would have (depending on the film) severe reciprocity failure, which would reduce the sensitivity even further than you had bargained for, not to mention an increase in contrast and (if colour) some strange colour shifts, perhaps to the point where only one of the colour layers worked at all. Pulling will get you the longer exposure without extra contrast and colour-shifting because it reduces the effects of reciprocity failure.

    You say you got an effective 16-stop filter factor from your foil filter, but Efke-25 has pretty heavy RF. Could well be that your FF is really 10 stops and you lost 6 stops to RF in your film. Hard to say.

    If you try with Acros, that has practically no RF (seems to need only one photon to activate it in most cases, so it remains stably activated when exposed at very low photon fluxes) even after an hour - about half a stop. Using Acros would give you a much better idea of the true FF achieved with the foil.

    New Ektar-100 (having tabular-grains like TMX/Acros but with dye couplers to give colour) is likewise very resistant to RF so if you want to shoot colour, it's a very good choice for avoiding colour shifts in long exposures. You may also find that the foil itself has a colour shift (it's designed for solar viewing, not general photography purposes), hence the suggestion of an ND400 which really is neutral.

    Edit: googling tells me that Baader solar foil is 5D (100,000) or about 16.5 stops so I guess you were right on that one. With reciprocity failure though on an old film like Efke-25, expect to see a much much longer exposure than 1e5 times the unfiltered.
    Last edited by polyglot; 02-28-2010 at 10:42 PM. Click to view previous post history.

  5. #15
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    This sounds like a perfect situation for three cameras, color separation filters, and some fairly heroic printing technology (unless, as a student, you qualify for a special indulgence permitting you to use d*****l methods). I may have to try this sometime, but if I go the non-analog route, I promise not to tell anyone

  6. #16

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    Well, I printed it. I honestly couldn't tell much difference between the 7 minute exposure and the 1 hour exposure.

    The only main difference is a giant greenish flare in the center. Like, it's really bad, I'll scan it tomorrow. Prof and classmates actually liked it a lot but I don't really. Which means there will be dual black and white and color images until I decide.

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