Old lenses with localized optics weak/issues

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fferreres Veteran Member • Posts: 6,861
Old lenses with localized optics weak/issues

It's probably something that has happened to many, and for me of course it's a similar situation. Sometimes, I get a very old lens, and it looks largely intact, but has some defect that affects performance.

One typical case, and I am not sure of the reason why it happens, is one of the elements showing lots of weak, like grind glass, in the outer edges. For me it's hard to explain why, other than hypothesis like being where dirt accumulated, or other guesses.

Does it makes sense in serious cases to create a baffle, or outer masking, or even paint that edge, if one really wants to have the lens perform more like the original? I thought about cutting out from some material, to make arbitrary, black mater disks (like a ring), but have no clue how to make them precisely, and scissors make for a very poor job. And often, the material would ideally be able to have some flexibility to accept a tiny bending to match the optic curvature.

I also used an acrylic pen in one, and the outcome wasn't bad. It's not at all perfect because it's more like 90% dark. I can get the paint out in the future if I want easily. And it helps with contrast a lot. I sometimes also mask a nick when it is located in the rear. I want to get Black 2.0 or 3.0, but I am not sure how I'd apply it.

Have you done something like this to make a lens maybe a little less "collectible" and more like what you actually want, restore it's performance even if some small trade off, like in the masking case, a tiny more vignetting but more of the original detail contrast?

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