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  1. #1
    Jeff Bannow's Avatar
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    Learning to work on lenses - where to start?

    I have a ziploc full of worthless enlarging lenses, and thought it might be nice to learn how to clean them. Is there a good primer on how to go about this? Maybe a walk through with photos from someone who disassembled a lens before?

    Any suggestions on needed tools? Suggested practice so I can reassemble this thing when I'm done?
    - Jeff (& sometimes Eva, too) - http://www.jeffbannow.com

  2. #2
    Nicholas Lindan's Avatar
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    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  3. #3
    Tel
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    Jeff,

    The thing about lenses is that each manufacturer had its own system for assembly. In general, there are likely to be a couple of threaded rings holding the whole thing together--one on the front and another on the rear. Typically, these will each have two slots or holes directly opposite each other to permit you to use a spanner wrench to turn them. Get a good spanner wrench (like the micro-tools ones) and not a cheap one. I always work on a small tray to keep parts from rolling onto the floor, and I always put a cloth on that when I'm working on a lens. Keep a notepad and pen handy to write reminders for reassembly. I learned from some professionals to use Glass Plus exclusively--it works better than any of the expensive lens cleaners and doesn't harm the coatings.

    Many of these lenses are simple designs, especially ones that don't involve shutters. Usually they are composed of two or three elements. I typically remove the front element, clean it carefully with a clean cloth and lens cleaner and then set it down to dry for a few minutes. (You don't want to trap moisture between the elements.) Then I replace the front, remove and clean the back element, and reassemble that. Taking the entire assembly apart at once just increases the chances that you'll forget how it goes together. If there's a middle element you can clean it from the front and the back without removing it: just put a piece of cloth over a cotton swab and clean it with that.

    Offhand I can't think of any good books or posts, though I'm sure there are some. I rely on a pretty good mechanical understanding and the knowledge gained from having messed up a lens or two and learning thereby what not to do.

    By the way (referencing the joke post in the previous reply) sometimes a yellow shift in lens color can be corrected by exposing the lens to sunlight. The trick is to put a piece of aluminum foil on the back of the lens and open the iris all the way (and the shutter, if it's part of the lens) and place the lens in sunlight (facing the sun) for a day or two, checking the color periodically as you do so. I'm sure this doesn't always work, but I don't know of any other purported cures.

  4. #4
    Jeff Bannow's Avatar
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    Quote Originally Posted by Nicholas Lindan View Post
    - Jeff (& sometimes Eva, too) - http://www.jeffbannow.com

  5. #5
    Jeff Bannow's Avatar
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    Quote Originally Posted by Tel View Post
    Jeff,

    The thing about lenses is that each manufacturer had its own system for assembly. In general, there are likely to be a couple of threaded rings holding the whole thing together--one on the front and another on the rear. Typically, these will each have two slots or holes directly opposite each other to permit you to use a spanner wrench to turn them. Get a good spanner wrench (like the micro-tools ones) and not a cheap one. I always work on a small tray to keep parts from rolling onto the floor, and I always put a cloth on that when I'm working on a lens. Keep a notepad and pen handy to write reminders for reassembly. I learned from some professionals to use Glass Plus exclusively--it works better than any of the expensive lens cleaners and doesn't harm the coatings.

    Many of these lenses are simple designs, especially ones that don't involve shutters. Usually they are composed of two or three elements. I typically remove the front element, clean it carefully with a clean cloth and lens cleaner and then set it down to dry for a few minutes. (You don't want to trap moisture between the elements.) Then I replace the front, remove and clean the back element, and reassemble that. Taking the entire assembly apart at once just increases the chances that you'll forget how it goes together. If there's a middle element you can clean it from the front and the back without removing it: just put a piece of cloth over a cotton swab and clean it with that.

    Offhand I can't think of any good books or posts, though I'm sure there are some. I rely on a pretty good mechanical understanding and the knowledge gained from having messed up a lens or two and learning thereby what not to do.

    By the way (referencing the joke post in the previous reply) sometimes a yellow shift in lens color can be corrected by exposing the lens to sunlight. The trick is to put a piece of aluminum foil on the back of the lens and open the iris all the way (and the shutter, if it's part of the lens) and place the lens in sunlight (facing the sun) for a day or two, checking the color periodically as you do so. I'm sure this doesn't always work, but I don't know of any other purported cures.
    Thanks - that helps a lot. What would you recommend for a spanner?
    - Jeff (& sometimes Eva, too) - http://www.jeffbannow.com

  6. #6

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    Quote Originally Posted by Jeff Bannow View Post
    I have a ziploc full of worthless enlarging lenses, and thought it might be nice to learn how to clean them. Is there a good primer on how to go about this? Maybe a walk through with photos from someone who disassembled a lens before?

    Any suggestions on needed tools? Suggested practice so I can reassemble this thing when I'm done?
    It really depends on the lens. I have a drawer full of enlarging lenses, most are basic lenses in barrel.

    The cells -- front and rear -- simply screw out of the barrel. Very often the only dirty surfaces are the front and rear (that face the paper and negative, respectively). Sometimes the surfaces that face the diaphragm also need to be cleaned.

    From here on things really depend on the lens. Most enlarging lenses are tessar types or plasmat types. One cell of a tessar type contains a cemented doublet, no further disassembly needed to clean. The other contains a pair of singlets. If the singlets' inner surfaces are dirty, try simply unscrewing the one that faces the diaphragm. This often works. A plasmat's cells contain a cemented doublet (faces out) and a singlet (faces the diaphragm). Again, very often the singlets simply unscrew.

    I wasn't clear. The singlets are often, not always, mounted in disks that screw into the cell. Screw back together to reassemble.

    I may not have been clear. Not all enlarging lenses are like the ones I know and had disassembled.

    Tools aren't often required, at least with my lenses.

  7. #7
    brucemuir's Avatar
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    Quote Originally Posted by Jeff Bannow View Post
    Thanks - that helps a lot. What would you recommend for a spanner?
    Look for one that has multiple tips/sizes that you can switch out.
    Then you are better prepared.

    Maybe some rubber "stopper" type things that will unscrew retaining rings/etc.
    These are more handy for slr lenses than enlarger lenses but still good to have.
    Also a flat rubber sheet like a mouse pad comes in handy.

    Micro tools sells the rubber stoppers but they were out of stock last I was there.

  8. #8
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    Quote Originally Posted by Nicholas Lindan View Post
    What this guy has done with this lens s about the most dangerous thing you can do with a lens that is known for having Thorium glass in it which is why it's yellow, and I hope he was wearing lead lined boxer shorts.
    Last edited by benjiboy; 06-28-2011 at 05:29 AM. Click to view previous post history.
    Ben

  9. #9
    Ian Grant's Avatar
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    Quote Originally Posted by benjiboy View Post
    What this guy has done with this lens s about the most dangerous thing you can do with a lens that is known for having Thorium glass in it which is why it's yellow, and I hope he was wearing lead lined boxer shorts.
    Ironically the repair to remove the yellowing is UV light or bright sunlight something thewre's no shortage of down under

    Ian

  10. #10
    Jeff Bannow's Avatar
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    Thanks everyone. Once I've mangled enough small lenses, I'll move on to the big stuff.
    - Jeff (& sometimes Eva, too) - http://www.jeffbannow.com

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