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  1. #31
    Ezzie's Avatar
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    Whatever you do make sure the camera and lens are absolutely light tight. The camera system will be exposed to infintely more light than the film per time unit than ever before. Leaks that have not shown up before will surely do so now.

    A film practically without reciprocity in normal use would be Acros 100, how it would perform under such conditions is anyone's guess.
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  2. #32
    RalphLambrecht's Avatar
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    Quote Originally Posted by Ezzie View Post
    ... A film practically without reciprocity in normal use would be Acros 100, how it would perform under such conditions is anyone's guess.
    Actually, Acros 100 has the best reciprocity of them all, I think.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  3. #33
    CBG
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    Quote Originally Posted by Stuggi View Post
    Yeah, but correct exposure is still going to be hard to nail down without any means of measuring the negative. What does one of those meters that measure negative density cost?
    I think a densitometer may be overkill. If the neg prints well, it's fine. But if it is off, as I think was noted earlier in this thread, you still can make a pretty good guess at how many stops will get you right. If you can compare your first test against some standard, you can make a good guess of the correction and get to a workable exposure with little time wasted.

    Knowing what a -say - four stop underexposure looks like would help you narrow your search much faster. Just compare a normally plus and minus exposed (in fractions of seconds or a minute rather than weeks and months) series from, I'm just pulling the number 5 out of the air, five stops under to five stops over against a super long exposure neg.

    Once you see you are off by about x number of stops, change your pack of neutral density to adjust the light hitting the film so you don't mess with the length of exposure - so as not to add one more variable...

    Getting a good workable basis for long exposures isn't rocket science.

    By the way, what are you trying to accomplish that can't be done with a shorter exposure? Also, I hope when you start getting results, that you'll post photos and info.

  4. #34
    Marco B's Avatar
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    Reciprocity failure test

    To give you some real data and numbers to crunch, I once did a more or less "controlled" reciprocity failure test by exposing Fuji Neopan Acros 100, Kodak TMax 400 and TXP 320 (about equals TriX 400, but 4x5" LF).

    I exposed the sheets for 30 minutes, 2 and 8 hours. The 30 minutes outside from a well illuminated building, the 2 and 8 hours in my bathroom darkroom, with the 2 hour exposure using a 40W halogen lamp shining against the opposite wall of the one I was photographing, and the 8 hours used the Ilford safe light (top of the image) shining downward and a small white bicycle LED light lying on my easel below the enlarger heads shining upwards.

    Please note, and this is not entirely ideal, that the images were created using a extreme wide angle Zero Image 4x5" LF pinhole camera with 25 mm "focal length" (depth of camera), which gives maybe something like a 120 degrees view.

    This also means there is large light fall-off, in the order of probably some 4-5 stops going from the exact centre of the pinhole to the sides of the negatives.

    Zero Image lists the pinhole camera as being F128, but this again is only valid in the exact centre of the image. To get a decent negative, that has some density at the borders of the negative, I usually expose it as an F256 minimum, sometimes even half a stop more. So F256 is probably a better baseline when judging it in relation to the resulting negatives presented here.

    I will post the results for the three different films in three separate posts as scanned negatives, as APUG allows only 5 images per post.

    Attached in this post are approximate EV values measured in each situation, using a ISO 320 setting on my spot meter.

    *** Please also note I probably overdeveloped the Fuji Neopan Acros 100 somewhat, and underdeveloped the other two films somewhat, maybe giving a false impression of Acros 100 having higher densities overall, while if you look at dark shadow detail, Kodak TMax 400 in the 2 and 8 hours exposures has more (e.g. lower part of washing machine and details in the radiator to the left of it). Another factor may be a differing amount of contrast increase with reciprocity failure, with Acros 100 having more contrast increase. IDK... ***

    My estimate for a possible break-even point between TMax 400 and Acros 100 based on this, and some quick and dirty calculations and assumptions based on Kodak's and Fuji's film datasheets, is something in the 6-8 hour range. Below that, you will have shorter exposure times with TMax 400 to get to a predefined negative density, above that probably with Acros 100. But it is hard to determine exactly without some "Ralph Lambrecht" style rigorous testing. I did just a quick and dirty test here... (Well, "quick" is maybe not the right word considering the overnight exposures )
    Attached Thumbnails Attached Thumbnails EV 30minutes.jpg   EV 2h.jpg   EV 8h.jpg  
    Last edited by Marco B; 01-14-2011 at 02:37 PM. Click to view previous post history.
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  5. #35
    Marco B's Avatar
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    Kodak TXP 320

    Kodak TXP 320

    *** Please note that the APUG image upload function mixes up images randomly.***:
    - The building facade is the 30 minutes exposure
    - The bathroom with visible washing machine is the 2 hours exposure
    - The bathroom with the burning safe light is the 8 hours exposure (least exposure on negative)
    Attached Thumbnails Attached Thumbnails Negative_Kodak_320TXP_2h.jpg   Negative_Kodak_320TXP_30min.jpg   Negative_Kodak_320TXP_8h.jpg  
    Last edited by Marco B; 01-14-2011 at 02:35 PM. Click to view previous post history.
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  6. #36
    Marco B's Avatar
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    Fuji Neopan Acros 100

    Fuji Neopan Acros 100

    *** Please note that the APUG image upload function mixes up images randomly.***:
    - The building facade is the 30 minutes exposure
    - The bathroom with visible washing machine is the 2 hours exposure
    - The bathroom with the burning safe light is the 8 hours exposure (least exposure on negative)
    Attached Thumbnails Attached Thumbnails Negative_Fuji_Neopan_Acros100_30min.jpg   Negative_Fuji_Neopan_Acros100_2h.jpg   Negative_Fuji_Neopan_Acros100_8h.jpg  
    Last edited by Marco B; 01-14-2011 at 02:35 PM. Click to view previous post history.
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  7. #37
    Marco B's Avatar
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    Kodak TMax 400

    Kodak TMax 400

    *** Please note that the APUG image upload function mixes up images randomly.***:
    - The building façade is the 30 minutes exposure
    - The bathroom with visible washing machine is the 2 hours exposure
    - The bathroom with the burning safe light is the 8 hours exposure (least exposure on negative)
    Attached Thumbnails Attached Thumbnails Negative_Kodak_TMax400_TMY_8h.jpg   Negative_Kodak_TMax400_TMY_30min.jpg   Negative_Kodak_TMax400_TMY_2h.jpg  
    Last edited by Marco B; 01-14-2011 at 02:34 PM. Click to view previous post history.
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  8. #38
    Marco B's Avatar
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    Lastly, the image attached here is from Fuji FP-50045B film, a 4x5" B&W instant film of Fuji with an ISO of 500. This was also a 30 minutes exposure.

    Marco
    Attached Thumbnails Attached Thumbnails Fuji_FP-500B45_instantfilm_30min.jpg  
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  9. #39
    Marco B's Avatar
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    Hi all,

    OK, so I decided to do some of my own "number-crunching" to get a "guess-timate" of the required ND filter set to keep a camera out for a few days.

    Let's make some assumptions first:

    - Film is TXP 320 or TriX 400 exposed at I.E. 320.
    - Aperture setting is F11
    - There is 12 hours of constant and relative good daylight (In this case, I think we can happily ignore the 12 hour night time exposure, as it will easily be more than 5 stops / EV values below the daytime exposure)
    - Average EV value for those 12 hours is EV12 at ISO 320.

    Now here's the guess-timation:

    - The pinhole camera was F256. Going from F256 to F11 is 9 stops
    - I measured an EV 0.7 at ISO 320 just below the safelight for the 8 hour exposure. I guess it is fair to say the average EV value for the room might have been something like EV 0.
    - From EV 0 under test conditions to EV 12 at day is 12 stops
    - 9 stops + 12 stops is 21 stops
    - Assuming we have ND8 neutral density filters, that are 3 stops each, it would require 7 ND8 filters (7x3 stops = 21 stops) to simulate the same EV 0 conditions of my bathroom with safelight under the average EV12 day light conditions.
    - Looking at my 8 hour exposure result of TXP320, I say the negative is some 3 stops underexposed.

    3 stops means the film should have had a 8 hours (test) -16-32- 64 hours exposure (not counting any extra reciprocity effects, if you would like to do that, at your own calculation factor).

    Now we only have 12 hours of daylight, so these 64 hours need to be multiplied by 2:
    2x64 = 128 hours = +/- 5 days

    So, my guess-timate is: Use TriX with 7 ND8 filters and expose for a minimum of 5 days at F11 if average light conditions during the day are EV 12 at ISO 320.

    If anyone sees a horrible error here, post a comment!

    Marco
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

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