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  1. #11

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    Well... as someone who has worked in an optical factory and has watched technicians stripping down and reassembling optics, I can tell you this:

    There isn't a lot of adjustment in most modern lenses. The glass sits in seats in threaded modules and these screw into precise register.

    Not so much older lenses, where the glass can be moved around with lens spanners in the mount to get the centring correct. With these I never take the glass out of the brass (or aluminium) mount.

    So... most lenses should go back together in the same registration and alignment as they started with.

    But. Big BUT.

    After reassembling the optic it would then be carefully tested for alignment just to check it was within spec. Usually it was - but it is possible a foreign body got under the seat or a spec of something stopped a thread from fully returning to it's register. The other possibility is just making a mistake - leaving a spacer out or putting a shim in on the wrong side. Occasionally this would happen and mean that something might be a little out of adjustment. Often it would just mean dismantling, cleaning the thread or seat and re-assembling again.

    But without the optical bench and calibration equipment - how would you spot this? You have no quality control check for reassembly errors.

    If I'm going to strip down a lens I at least take some pictures of a test chart or something first - so after reassembly you can check the before and after and see whether you've trashed the performance.

    Although personally, my rule of thumb is to dismantle as little as you need to to do whatever you need to do... For most jobs the problem is usually replacing lube - which doesn't require too much dismantling of the optical parts of the lens - or removal of dust, which maybe just requires a front element taking off or something.
    Steve

  2. #12
    clayne's Avatar
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    Quote Originally Posted by David Lyga View Post
    What you REALLY have to beware of are the short lenses like 28mm or, worse, 24mm. These are VERY complex as to how the elements are put together and, just as important, which SIDE of the element is to be placed.
    Are you specifically talking floating-element or CRC lenses? I'd think the same level of attention to detail would hold for any lens (strict order and up/down orientation being followed). Is there something specific you meant by "side" of the element? I'd think that one would never willy-nilly flip an element regardless of it being an 18mm or a 50mm lens but wanted to understand if you meant something else.
    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

  3. #13

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    Quote Originally Posted by David Lyga View Post
    ...Vaseline...
    My experience with Vaseline (coating battery terminals on my car) is that it runs like the devil. Something you want when water/acid-proofing terminals and stranded wire, but something I would think you don't want when dealing with lenses. I would opt for some hi-tech silicone grease that stays where you put it. Shouldn't cost a fortune, if you look at an industrial supply company instead of some specialist optics supply place.

  4. #14

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    Helical grease is not a lubricating grease.. it is dampening grease intended to give resistance... as you can see MicroTools is rated Medium n Light grades.

    Vasaline is not a good choice of lubricating medium as it gets watery n runs in heat as well as out gas over time, that in a lens is a bad mix.

    Before lifting an element, mark the top surface with a magic marker and use a small suction cup to get it up. Clean the marker off last before it goes back in so you don't make the mistake of flipping it wrong side up.

    .
    Anyone can make a Digital print, but only a photographer can make a photograph.

  5. #15
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    I have worked on a few lenses/ shutters in various sizes. I never worrried too much as well either. Just simple unscrewing, cleaning, and rescrewing it back. I just worked on two a few days ago. But I never worked on any that were too complex. I have done small range finders, TLRs, primes, and zooms.

    Its not too hard, just organize and keep track of parts and use common sense and/or guides.

  6. #16
    clayne's Avatar
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    Quote Originally Posted by jordanstarr View Post
    You're not missing much, if anything at all. Every lens I've ever taken apart has been relatively simple. If it wasn't, it was because the lens itself was being difficult (ie. parts refusing to be unthreaded). I think a lot of it has to do with a cash grab -make it seem so overly complicated and daunting that you must seek professional help. It's the same thing with cars. Go to a mechanic and tell them you've never done an oil change before and they'll try to talk you out of it, say you need all these tools and all the things you could do to ruin your car, etc etc. and that you need to pay them to do it.
    As a person who's rebuilt engines on my own and of course heard the common lines along "you'll shoot your eye out!" I can attest to this type of thing.

    Some people also just hear rhetoric like "NEVER TAKE APART A LEICA LENS!! THE PRECISION IS SO PRECISE AND THE SECOND IT COMES APART YOU'VE KNOCKED IT OUT OF WHACK!!!" and then just repeat it all over forums without having a clue what they're talking about. Well, I've taken apart nearly every lens I've ever owned and even some with built in shutters that weren't working and fixed them without a manual or anything. I've taken apart all my Leica lenses (28mm, 35mm, 50mm), some canon rangefinder ones for cleaning, etc. and they still take sharp and beautiful photographs.
    Yep the Leicaphiles seem to be particularly paranoid about this - but they also believe there is an implicit magic in both the cameras and lenses (disclaimer: I do love my M4+Summicron). Speaking of which, I might have to crack open the Summicron as oil on the blades has migrated to the rear element and I'm not really into the whole diffusion effect. Any gotchas I should know about? As you can probably tell, there is zero documentation out there (only the chosen ones are allowed to fix these lenses).
    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

  7. #17

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    Most Carl Zeiss, Jena lenses (pre. about mid '70s) and Meyer and Pentacon lenses DO have an offset adjustment for the rear element/s. This is best left alone unless you have to strip them to clean fungus, and if you do, you need to try very hard to re-assemble them exactly as you found them.

  8. #18

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    Quote Originally Posted by clayne View Post
    As a person who's rebuilt engines on my own and of course heard the common lines along "you'll shoot your eye out!" I can attest to this type of thing.



    Yep the Leicaphiles seem to be particularly paranoid about this - but they also believe there is an implicit magic in both the cameras and lenses (disclaimer: I do love my M4+Summicron). Speaking of which, I might have to crack open the Summicron as oil on the blades has migrated to the rear element and I'm not really into the whole diffusion effect. Any gotchas I should know about? As you can probably tell, there is zero documentation out there (only the chosen ones are allowed to fix these lenses).
    Which Summicron? I have to take my 8 element 35 apart every once in a while to clean out a very slight haze that builds up. It is straightforward, but there are a couple shims to make note of. I seem to recall that the 6 element 35 was very simple. The 50 DR is also straightforward as best I remember, I haven't had any reason to take my newer 50 apart so don't know much about that.

  9. #19
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    Quote Originally Posted by Mark Crabtree View Post
    Which Summicron? I have to take my 8 element 35 apart every once in a while to clean out a very slight haze that builds up. It is straightforward, but there are a couple shims to make note of. I seem to recall that the 6 element 35 was very simple. The 50 DR is also straightforward as best I remember, I haven't had any reason to take my newer 50 apart so don't know much about that.
    Hey Mark, it's a summicron 35 v4. The latest one before ASPH.

    Basically oil has seeped out past the blades and onto the inside of the rear group.
    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

  10. #20

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    Quote Originally Posted by clayne View Post
    Hey Mark, it's a summicron 35 v4. The latest one before ASPH.

    Basically oil has seeped out past the blades and onto the inside of the rear group.
    One warning - You could be getting into the time frame when the optical unit was glued into the focusing mount. I really don't know for sure on yours.

    On my earlier 35 Summicron there is a retainer in the rear that holds the optical unit into the focusing mount. Take off the retainer and pull out the unit. Then, I believe, the rear will just unscrew and get what you need. I think the 6 element version just before yours was the same.

    If yours isn't held together that way, you may still be able to unscrew the rear optical cell without disassembling the lens. Probably not much to get a grip on though (pieces of bicycle inner tube are handy grippers). If there is a single retainer slotted for a spanner in the rear, it will likely only get you the last element or cemented group, but sometimes is tight enough that the whole cell will unscrew.

    If you don't like the situation when you look it over, Sherry Krauter is very good for this. Edit - Oops, I see that would not be convenient from your location.

    If someone is more familiar with this particular lens, hopefully they'll speak up. I've only had that version in my possession for a couple weeks several years back.

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