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  1. #1
    BetterSense's Avatar
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    negative bowing/warping

    I just realized that if I focus a 'cool' negative on the baseboard, that after about 10s with the enlarger on, my 4x5 negatives warp out of focus.

    The solution seems to be to keep the exposure times under 10s, or to use a glass negative carrier, or to let the negative warm up and stabilize before making the exposure. Will the negative stabilize if I leave it in there for a few minutes?
    f/22 and be there.

  2. #2

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    Good Morning, Better Sense,

    By the time you have focused and worked on the exact print composition, the negative should have had more than enough time for any "popping." The few seconds of "Off" time required for putting a sheet of paper in place shouldn't have any reverse effect.

    You don't mention the type of enlarger you're using. Should it happen to be a Beseler 45, locate a Negatrans carrier. That carrier grips opposing sides of a negative, keeping it as flat as a glass carrier would. Actually, I'd be surprised if your enlarger is a Beseler 45, since I never experience a "popping" problem with mine even when not using the Negatrans.

    Unless you're printing with the lens wide open or maybe at f8, depth of field may hide the problem anyway. Theoretically, using a small lens opening leads to diffraction while it increases apparent depth of field, but you may detect little or no visible effect with a good-quality lens. If you need f22 and a 20-25" exposure, would that really be a problem?

    Konical

  3. #3
    BetterSense's Avatar
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    I have an Omega D2. I only noticed the problem recently when I was making an extreme enlargement that required a medium aperture and 40s exposure. Smaller prints only require ~10s exposures at f/22, so I don't think this will be a problem for the most part. I usually try to minimize enlarger 'on-time' both to save the bulb and to cut down on light in the darkroom.
    f/22 and be there.

  4. #4
    Robert Hall's Avatar
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    As a suggestion,

    You may look for a piece of glass that some enlargers have as an option to keep the heat from affecting neg flatness as well.

    I get this on my Beseler 23CIII and put the heat glass in there, never a problem since.
    Robert Hall
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    Technology is not a panacea. It alone will not move your art forward. Only through developing your own aesthetic - free from the tools that create it - can you find new dimension to your work.

  5. #5

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    I too had the problem you describe when enlarging 120 with my D2V. After many months of preheating the negative then quickly sliding paper into my easel I finally installed heat absorbing glass in the VC head. That ended the "popping" problem. Never had the patience to deal with glass carriers. While I never heated the negative "for a few minutes" my bet is the negative would pop back just as quickly even with the extended heat time.

  6. #6
    BetterSense's Avatar
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    Well on my enlarger, the condenser lenses extend down nearly to the negative itself. Any heat absorbing glass would have to go on top the condensers.
    f/22 and be there.

  7. #7

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    Good Morning, Better Sense,

    I'm not familiar with the D2V, so I may be way off base here. Doesn't it have a tray for VC filters somewhere above or between the condensers? On the Beseler 45 the HAG is an integral part of that tray which slides into position between the condensers. As on your enlarger, the bottom condenser sits quite near the negative when the head is adjusted for 4 x 5 negatives.

    Konical

  8. #8
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    Semi-unrelated, but 10s @ f/22 w/ smaller prints? That must be a seriously bright light source. I'm usually around 8-16s @ f/8-f/11 w/ 5x7 on my Kaiser. However, I haven't really cranked the light source up to the max as I'm comfortable with the medium length times.
    Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.

    http://www.flickr.com/kediwah

  9. #9

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    Good Morning,

    The term "smaller prints" is open to interpretation, of course, but 10" at f22 would not be grossly out of line for printing a 4 x 5 negative to 8 x 10 on, say, Ilford MG with a #2 or #3 filter. A lot would depend on the density of any particular negative and the paper used. For a given print size, print exposures from 4 x 5 negatives tend to be rather short compared to those from smaller negatives.

    Konical

  10. #10
    clayne's Avatar
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    Quote Originally Posted by Konical View Post
    For a given print size, print exposures from 4 x 5 negatives tend to be rather short compared to those from smaller negatives.

    Konical
    Good point. Completely glossed over the 4x5 point.
    Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.

    http://www.flickr.com/kediwah

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