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I recently picked up an Olympus OMZ 50mm f1.8 pretty cheaply of ebay. The front element has a slight mould on the rear side although so far I've not seen this affect the image quality.

Disassembling the lens, the front three elements are part of one block. As on the parts diagram here:

enter image description here

How would I disassemble this to clean the rear side of the front element? I'm aware that it's not designed to be disassembled, and that it might be inadvisable to do it. But I'm very interested to hear what the best way to do this would be, providing the right equipment was available.

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    If this is the first lens that you are going to disassemble, you should know that there is a big chance that you'll accidentally destroy it. – Agares Feb 5 '15 at 19:54
  • There's a post here that might be of help: forum.mflenses.com/zuiko-50mm-f1-8-strip-t19498.html – Blrfl Feb 6 '15 at 13:27
  • And, of course, a youtube video: youtube.com/watch?v=aj0S55-aXjQ You have a spanner wrench, right? – inkista Feb 6 '15 at 20:28
  • I've got a spanner wrench and I can disassemble and reassemble the lens fine. The trick is, how could I disassemble the part that isn't supposed to be disassembled? The part in the diagram has three elements in one block. I don't know if they're glued or just an interference fit. – Slipstream Feb 8 '15 at 17:09
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Don't know Olympus construction but Canon is using plastic rings which holds lens elements and these rings are glued together (most probably ultrasonic welded). You can disassembly that by lathe with precision approach but question is how you will assemble it concentric.

  • Thanks for the practical answer, lathing a lens sounds like a relatively delicate operation. Have you seen any guides or videos of someone doing something similar to this? I'd be really interested to see what tools they use, and how they catch the lens once it's free. – Slipstream Apr 10 '15 at 8:35
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The complexity in disassembling a lens is not necessarily only in the disassembly (however there are indeed potential pitfalls there). The biggest question you should be asking yourself is: Can you recollimate it once you've cleaned the lens and reassembled it? With a single element removal, you might be fine, but if you disassemble more than that, you might want to consider how you would realign everything.

You cannot simply reassemble the lens after cleaning. You have to reassemble it with every element exactly centered relative to all the rest, relative to the diaphragm/aperture, etc. It only takes minute offsets in shift or tilt that will lead to poorer optical quality. Older lenses may be easier to disassemble and reassemble without the need for some kind of optical test bench to realign everything, but realignment is part of the process, and usually requires some kind of special setup.

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    Thanks for the detailed answer, two followup questions: Do you know what kind of special set up would normally be used for this? What degree of accuracy are the lenses normally aligned (what order of magnitue? 10um, micron, submicron?) – Slipstream Mar 21 '15 at 12:57

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