longest exposure time.

Discussion in 'B&W: Film, Paper, Chemistry' started by dreamingartemis, Jan 17, 2012.

  1. dreamingartemis

    dreamingartemis Member

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    Hi,
    Just wanted to see if anyone has encountered situations where they had to exposed their negs using an enlarger for an insane amount of time because the negs were thick.

    Let me start off first, I've only been doing this for a while but last night I was doing a printing job for a client and had been doing test strips. But for the life of me, I couldn't get the blacks or whites, just very faded grey. I keep increasing the time and even bumped the filter to 5 and still, it was dull grey.

    I had reached 150 seconds when I decided "screw this, I'm pushing it to 200 seconds". Finally the blacks and white showed up correctly and so decided to do a full print, to my horror when the image showed up, while one side was properly exposure but the right side wasn't, I looked at the negs again careful and noted that there was definitely a tree there (the photos was a picture of 2 trees, the left tree was now properly exposed but the right one was under!).

    Realizing that the only way I was going to get a properly a exposed print, I did a test on the right side. Even 200 seconds wasn't enough, it took up to at least 400 and the aperture on the lens was as wide as it could go! So now printing it was going to be a 2 fold operation, first I had to exposed the whole print for 200 seconds, then burn the right side (the second tree) for an additional 200 seconds!

    So here I was, in the darkroom, with 2 cardboards dodging and burning the photo just to get it properly for over 400 seconds. While it wasn't something to talk about but I felt pretty happy at my first attempt and hopefully the client will be happy.

    I've heard of people who had to sometimes exposed for 30 minutes before, has anyone does such a thing before? Or is there some other way I could have avoid the problem of doing such long exposure?
     
    Last edited by a moderator: Jan 17, 2012
  2. Andrew K

    Andrew K Subscriber

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    My record for printing black and white was 8 minutes for the basic exposure, plus a couple of minutes burning in...it was a bit of a crop though, as the enlarger was about 8ft from the printing paper

    Although when I was prinitng Cibachromes I can remember having to use an enlarger with the wrong mixing box....45 minute exposure for a 60 x 40 inch print!

    And maybe not the longest time, but around 15 years ago I ran a customer black and white lab, and was asked to contact print some glass plates...they were so dense that my exposures were done by firing a Metz 45 flash 5 times on manual from about 1ft to get a correctly exposed print....
     
  3. Vaughn

    Vaughn Subscriber

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    Ten hours for a carbon print under a 175W merc vapor lamp. The previous 6 hour exposure was the better print, though. :D

    I have worked on a silver print for 15 minutes -- but the base exposure was 25 seconds and the rest was burning in...
     
  4. dreamingartemis

    dreamingartemis Member

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    Holy crap! 45 minutes and 5 minutes with flash for another job?! You should have charged for "work hazard"!
     
  5. dreamingartemis

    dreamingartemis Member

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    .....how did you even determined the exposure time? Either you guessed it right or there was a lot of test strips.......10 hours......:blink::blink:
     
  6. keithwms

    keithwms Member

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    Well why not first dupe the thick neg onto something much more sensitive e.g. film. The problem here is that you have an ~ISO 3 material. You can dupe it to film and rate that film at whatever you please.
     
  7. NormG

    NormG Member

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    Do these long exposure times have any effect on the negative in the carrier? The reason i ask is that i recall somebody once commenting on an out of focus print because the negative warped due to the heat from the lamp.
     
  8. dreamingartemis

    dreamingartemis Member

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    I guess I could expose it to a medium format film instead that has a higher ISO rating. but I would have to do it in pitch darkness
     
  9. dreamingartemis

    dreamingartemis Member

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    An excellent question....any takers?
     
  10. Vaughn

    Vaughn Subscriber

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    I would heat the negative up in the enlarger of about a minute (by turning the lamp on) and let the negative "pop". I then would start my exposure. I would keep the enlarger on during the 15 minutes or so of burning.

    Others use a glass negative carrier.

    The 10 hr exposure:

    No test strips. My average exposure time was two hours. This particular neg had a large area of high density (sun on granite -- I could barely make out detail in the highlights with an intense light behind it) so I just exposed a bit more than a stop more -- 6 hours. The print looked very good, but I though I would add just a little more than a half-stop more exposure to see what it looked like...ten hours.
     
  11. dreamingartemis

    dreamingartemis Member

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    You have very thick negatives if your average time is 2 hours........:cool:
     
  12. piu58

    piu58 Member

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    I always establish my exposure plan with not so large paper, mostly 18x24 cm². Times are much shorter then. Of course I need a test strip for the large paper for finding the exposure time and slight corrections of contrast, but the relations between the image parts remain the same, if I use the same type of paper. If you'd use identical paper, that means, if you cut a large format int smaller ones, you don't need to correct the contrast.
     
  13. michael_r

    michael_r Subscriber

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    In my opinion unless there is zero heat buildup at the negative stage over such a long period, a glass carrier is necessary. I would not rely on preheating the negative. At a minimum I suggest a top glass carrier (glass only on top of the negative) if you don't want to use a full glass carrier. Negative deformation from heat is mostly in the upward direction so a top glass can help quite a lot.

    An important benefit to using a glass carrier is it often enables you to use a larger aperture on the enlarging lens, which can significantly shorten the exposure time.

    Even with a glass carrier, I would do some tests without a negative just to see how much heat buildup there is during a very long exposure. In many setups, even with heat absorbing glass etc, tremendous amounts of heat can build up at the negative stage and you don't want to damage anything.
     
  14. Andrew K

    Andrew K Subscriber

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    In my case I didn't do dupe positives because I was printing 100 year old wet plate negs ...and the tonal range on unfiltered multigrade paper was incredible....
     
  15. Andrew K

    Andrew K Subscriber

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    it can depending on your enlarger. If I'm using a condensor enlarger I tend to use at least a anti-newton glass above the neg (which seems to prevent popping). On a diffusion enlarger (either an enlarger with a color head - usually a De Vere 504 or Chromega, or an enlarger fitted with a Ilford Multigrade 500 head) I've always used glassless carriers and not had any neg popping problems with long exposures

    Then again if I were printing anything bigger than 6x7, or a single negative I would probably use a glass carrier
     
  16. dreamingartemis

    dreamingartemis Member

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    Yeah, that's what I'm doing now because of this photo. First I would look at it on the lighttable, if it looks thick, prepare up square pieces from one large piece, then place each small piece of squares on the area or region of the photos that matters to the overall composition. Guess the exposure first base on past experience, develop and if it doesn't look right, try again. Do this till it looks right, only then do a final print.....

    But even with all that, it's still all art and not science :laugh::laugh: since mistakes can still happen as I learned last night when I again wasted some 9.5x12 inch FB paper