Exposure incrementally or all at once?

Discussion in 'Enlarging' started by fralexis, Nov 20, 2013.

  1. fralexis

    fralexis Member

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    I had been taught long ago that final exposure should follow the same series of short exposures as the test strips...ie, for a total exposure of 20 seconds, expose in 5 second increments rather than the full 20 seconds. It seems to me that perhaps the full 20 seconds would be preferable to give time for dodging and burning. What do you do? Thanks.

    Alexis
     
  2. Bill Burk

    Bill Burk Subscriber

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    Shoot, now you have me second-guessing my final print exposure method.

    I make test strips in one long time exposure. I expose a sliver of test strip and uncover strips throughout leaving the "5" second strip for last... Because my light source is uncontrolled fluorescent, it is most likely to start dim and brighten during a 40 second exposure. So... If I were to follow your advice, I'd have to leave the timer at 40 seconds for the final print with the lens covered until the selected time on the countdown. Then I should uncover to expose paper for the remaining time on the timer... Or I should revise my strip exposure method to give the 5 seconds first and cover up small sections of the strip as time progresses - the way all the references say to do it.

    Now I know why.

    But in practice, when everything is dry, I don't find THAT much difference between the selected test strip compared to the final print.
     
  3. MSchuler

    MSchuler Subscriber

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    I've read in a few places that the values of text strips is not exact because of the warm-up time for the bulb. However, since it is just a test strip, I'm not sure of the need to account for this. Has anyone quantified how much less dense the darkest portion of a test strip is compared to a straight exposure for the same nominal duration?

    When I am making a fine print, I typically make test prints 1/8 stop lighter and darker than the final target and, after everything has dried completely (overnight, if not longer), I judge whether the target density is what I really want and adjust accordingly.
     
  4. NedL

    NedL Subscriber

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    I use a metronome as my timer and to make test strips I move a card incrementally to block more and more of the strip. So the "20 second" section of my test strip actually receives a continuous 20 second exposure, as would the final print. So for me this would not make sense. I don't know what others here do...
     
  5. Bill Burk

    Bill Burk Subscriber

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    NedL,

    You're doing it right. Assuming there is a warm-up period, both your test strip and final print have times that include the warm-up.
     
  6. NedL

    NedL Subscriber

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    Oh hi Bill! Somehow I hadn't seen your post when I responded to this thread, but it prompted a PM when I did read it. I think with a 40 second exposure you will have a warm-up and then a period of quite steady light. The length of the warm-up will depend on the temperature at the start which increases as you use your enlarger. And even back-to-back test strip then final print could have slightly different proportion of that 40 seconds being in the warm-up stage. If we were talking about a 2 or 3 minute exposure, the peak brightness would occur in the middle somewhere ( probably around 20 seconds ), so it gets even more complicated! Hopefully my PM makes sense... it would be obvious if I could show you a couple of graphs.
     
  7. Bill Burk

    Bill Burk Subscriber

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    Hey Ned,

    I was wondering when you found the time to write... That was quick.

    I have a routine that "compensates" for these issues fairly well, but not perfectly. And you're right, the reason it probably works fairly consistently for me is that I allow warmup as part of the routine.

    Alexis,

    If you are using a regular Tungsten light source, you probably have no issues significant to worry about. Ned and I have flourescent lights that really do brighten significantly in the first few seconds if you turn them on when they're cold.
     
  8. markbarendt

    markbarendt Subscriber

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    I use one continuous exposure.

    On the rare occasion that I do test strips any more I do them with one exposure, sliding a card over the paper to control time.

    A meter has replaced the role of the test strip.
     
    Last edited by a moderator: Nov 21, 2013
  9. Doremus Scudder

    Doremus Scudder Member

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    Exactly what I do.

    I also let the enlarger lamp warm up a bit before beginning exposure (halogen lamps in a dichroic head) or use a stabilizer (cold-light). With dichroic heads I hold a card below the lens, switch on the timer/metronome and count off 5 or 10 seconds before beginning my test strip or exposure to at least get the initial warm-up phase behind me before I start the exposure. This I do every time, so any further variance is fairly consistent.

    FWIW, I can't imagine trying to dodge using Fred Picker's series of 3-second bursts... I like a continuous exposure.

    When using a cold-light head before I had a stabilizer I simply left the thing on for the entire printing session, covering the lens with a cap between exposures so that light stability was not an issue. I only burned out one tube in 10+ years that way.

    Best,

    Doremus
     
  10. bdial

    bdial Subscriber

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    I've done test strips both ways, continuous using a card to block the light, and with on-off increments.
    Currently I use the on-off method because the timer I now use is programed for that.

    Both methods work, I've not noticed a difference, but I've never tried to make a comprehensive comparison either.

    I think that in practice any differences get taken care of by the total workflow. That is, you make a test strip, determine a best choice exposure, make a print and then tweak things until it's right, by some combination of exposure adjustment and dodging and burning. Step one is to pick a method and use it.

    FWIW2, yeah, I agree regarding the "Fred Picker" method.
     
  11. Maris

    Maris Member

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    I find a difference between giving 10x2 second exposures and giving a single 20 second exposure with my Omega D2V enlarger fitted with a 75 watt Photocresenta bulb.

    The intermittent exposure sequence includes 40 moments when the bulb is dim and red and non-actinic and 20 intervals when it is bright and actinic. But the difference is surprisingly (!) small. The resultant gelatin-silver photographs from either method can be eye-matched by a small change in room lighting. In practice the time adjustment I give to compensate for final dry-down (typically 8%) swallows the small intermittency effect.
     
    Last edited by a moderator: Nov 21, 2013
  12. ROL

    ROL Member

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    For me, it depends mostly on your tools and individual working style, but for the record I've never experienced any qualitative difference employing either style of printing. That may be because my exposures are always quite lengthy, any small differences in the amount of light delivered to the paper being ultimately negligible. Where it can make a difference is in the ability to keep track of dodges (particularly) and burns incrementally (i.e., 10 x 6 secs (total exposure) – 2 x 6 secs (dodge first area) – 1 x 6 secs (dodge second area) + 15 x 6 secs burn, and so on). Combined with a footswitch for the enlarger, one never needs to interrupt the process, or take eyes off the print during exposure.