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  1. #1
    Vincent Brady's Avatar
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    Fogging of enlarging lens

    I have being using a Durst M670 BW for several years but have recently encountered a fogging problem with the enlarging lens.
    1. I insert my neg and turn on the enlarger and compose my image.
    2. When satisfied I turn it off and get a test strip and put it into position.
    3. I set my f stop timer for test strips.
    4. I switch on to start the sequence only to discover that the lens has misted over. It is the upper glass element nearest the neg. that has fogged over. This requires me to remove it and dry it off.

    I have being using this lens and enlarger for several years with out encountering this problem.

    Any ideas or suggestions ?

    TEX

  2. #2
    Photo Engineer's Avatar
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    Too much Irish mist?

    Sorry, I can't help but I could not resist that either.

    PE

  3. #3
    ic-racer's Avatar
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    I had a 8mm projector I refurbished that would do this. I suspect your Durst is generating some good amount of heat somewhere?

  4. #4
    wiltw's Avatar
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    Have you attempted to seal the lens in an airtight container in which silica gel has been placed, and let it sit in that for a good amount of time?

  5. #5
    Vaughn's Avatar
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    Perhaps some of that silicate whatever (the packets that absorbs moisture) should be put inside the bellows while the enlarger is not in use. Excessive moisture in your darkroom, combined with heat = fog..

    Or perhaps just turn on the enlarger for awhile before use with the lens off.

    My 8x10 camera does this whenever I set it up in the sun (a rarity in my part of the world, but not when I go up to Yosemite or similar places). Under the darkcloth I can see the image start to fuzz up. The sun heats up the bellows, drives the moisture out, and fogs up the lens. It is not that I take the camera out in the rain and get the bellows wet -- it is just the moisture in the air over time.

    vaughn

    PS...if your darkroom is that moist, you might consider keeping the lens in a dry place, too (or do what wiltw suggests) -- we lose enlarger lenses to mold all the time. Sometimes I can clean the mold off, but sometimes it is inbetween where I can't get to it.
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  6. #6

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    Humidity in negative?

    I read in a different posting {negative flatness}, maybe on a different forum, that negatives in your climate [might] absorb moisture in the emulsion when the weather is damp [one poster said: 9+ months of the year there]. Then the heat from the enlarger bulb drives the moisture out of the negative. Perhaps this moisture then condenses on the lens.

    Suggestions: [a] Heat the lens. Put a low-wattage bulb nearby, and keep that on between exposures. OR:
    [b] Ventilate the lens. Use a tiny computer "muffin" fan. Turn it off during exposures [vibration]. OR:
    [c] Keep negatives drier. Store in a warm place, or in a compartment with desiccant.

  7. #7
    bowzart's Avatar
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    As the previous poster suggests, heating the lens would most likely work. One easy way to do that would be to remove the lens and keep it in the living area when it's not in use. Or you could keep the darkroom heated to the temperature that you'd normally keep the rest of the house for living and hold it close to constant. Either should work.

  8. #8
    Vaughn's Avatar
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    Tex, does this happen only when you first use the enlarger for the day, or every time you use a new negative? Personally, I can't see how a negative could contain enough moisture to fog a lens...but I have been wrong before!
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  9. #9

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    My darkroom/dark-cupboard is off the bedroom, which isn't heated. Whenever I have a printing session in the cold weather I switch on the enlarger with the lens in place for about ten minutes whilst I'm mixing up chemicals, wondering what I've done with the print tongs, etc.. The fog forms (with no neg in place) but soon disappears and stays away for the rest of the session.
    Steve

  10. #10
    Ian Grant's Avatar
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    Back in the 80's I had this problem regularly, the best solution is as already suggested keep the lenses outside the darkroom in the warm & dry.

    One consequence of allowing it to continue is that every time you get condensation then dry it out there's a fine coating of airborne dust left on the inner lens surfaces, this builds up and can happen between elements that can't be cleaned, this causes haze and ultimately means writing off your lenses or an expensive service.

    Ian

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