negative bowing/warping

Discussion in 'Enlarging' started by BetterSense, Nov 5, 2009.

  1. BetterSense

    BetterSense Member

    Messages:
    3,126
    Joined:
    Aug 16, 2008
    Location:
    North Caroli
    Shooter:
    35mm
    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?
     
  2. Konical

    Konical Subscriber

    Messages:
    1,702
    Joined:
    Jun 1, 2003
    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. BetterSense

    BetterSense Member

    Messages:
    3,126
    Joined:
    Aug 16, 2008
    Location:
    North Caroli
    Shooter:
    35mm
    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.
     
  4. Robert Hall

    Robert Hall Subscriber

    Messages:
    2,047
    Joined:
    Aug 18, 2004
    Location:
    Lehi, Utah
    Shooter:
    ULarge Format
    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.
     
  5. Rick Jones

    Rick Jones Member

    Messages:
    116
    Joined:
    Feb 9, 2004
    Location:
    Maryland
    Shooter:
    Multi Format
    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. BetterSense

    BetterSense Member

    Messages:
    3,126
    Joined:
    Aug 16, 2008
    Location:
    North Caroli
    Shooter:
    35mm
    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.
     
  7. Konical

    Konical Subscriber

    Messages:
    1,702
    Joined:
    Jun 1, 2003
    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. clayne

    clayne Member

    Messages:
    2,837
    Joined:
    Sep 4, 2008
    Location:
    San Francisc
    Shooter:
    Multi Format
    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.
     
  9. Konical

    Konical Subscriber

    Messages:
    1,702
    Joined:
    Jun 1, 2003
    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. clayne

    clayne Member

    Messages:
    2,837
    Joined:
    Sep 4, 2008
    Location:
    San Francisc
    Shooter:
    Multi Format
    Good point. Completely glossed over the 4x5 point. :wink:
     
  11. bdial

    bdial Subscriber

    Messages:
    5,411
    Joined:
    Jan 2, 2005
    Location:
    NE U.S.
    Shooter:
    Multi Format
    In a D2 I think the heat absorbing glass goes above the condensers, in the base of the lamp house.

    It's recommended by Omega if you use the higher wattage lamp.
     
  12. BetterSense

    BetterSense Member

    Messages:
    3,126
    Joined:
    Aug 16, 2008
    Location:
    North Caroli
    Shooter:
    35mm
    Is the glass anything special, or will a sheet of regular old soda glass work?
     
  13. Ronald Moravec

    Ronald Moravec Member

    Messages:
    1,239
    Joined:
    Jan 17, 2005
    Location:
    Downers Grov
    The D series is designed for only 75 watt bulb. Add the heat absorbing glass after that.

    Make sure the head cooling vents are open.

    I have the Aristo dimmer for their cold light. It works for incandescent also. Turn the wattage down and you get less light and heat.

    Before the aristo, I used a wall 4 outlet box and installed a light dimmer

    The Aristo is a very well made piece that reminds me of 1930 technology. Pay what it takes to get one as. nothing is made this well today.
     
  14. Martin Aislabie

    Martin Aislabie Subscriber

    Messages:
    1,416
    Joined:
    Nov 17, 2007
    Location:
    Stratford-up
    Shooter:
    4x5 Format
    Yes, heat absorbing glass is special

    You will have to buy the appropriate peice of glass to suit your enlarger

    Martin
     
  15. jvo

    jvo Subscriber

    Messages:
    466
    Joined:
    Dec 6, 2008
    Location:
    left coast of east coast
    Shooter:
    Medium Format
    bulb....

    i have a d2 (not v). I have a cold light head no problem.

    I replaced the condenser head - it had a piece of glass under the condensers and above the negatives. the bulb is so far away I don't see how heat could be a problem. Is the d2v that different?

    email harry taylor (harry_g_taylor@sbcglobal.net) - he is an omega expert - refurbishes and rebuilds them. he'll know.

    good luck
     
  16. Lew1716

    Lew1716 Member

    Messages:
    5
    Joined:
    Oct 15, 2009
    Shooter:
    35mm
    As another poster notes, you can obtain a heat absorbing glass for your enlarger. Omega, did in fact make one & you should be able to get it from KBH.
     
  17. bobwysiwyg

    bobwysiwyg Subscriber

    Messages:
    1,623
    Joined:
    Mar 28, 2008
    Location:
    Ann Arbor, M
    Shooter:
    Multi Format
    Just curious, this 'heat absorbing glass,' is it the same sort of thing used in some windows to cut down on UV light?
     
  18. BetterSense

    BetterSense Member

    Messages:
    3,126
    Joined:
    Aug 16, 2008
    Location:
    North Caroli
    Shooter:
    35mm
    I think it needs to block IR light. Even so, there may be films on sale that block or reflect IR for energy savings. I should look into that.