Old Perma-Cel vs modern foam shims for lens centering

I tried using those new foam shims from China on a Canon 50mm f1.4 rebuild and they compressed way too much under the retaining ring. Went back to the original Perma-Cel fiber shims from the 70s and the collimation held dead steady after 3 test cycles at different temperatures. Has anyone else noticed the foam stuff just doesn't hold up like the old paper based shims?

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johnh823mo ago

Honestly, those old Perma-Cel shims are like finding a vintage tube of Helios glue that still works perfectly. Ngl, I've got a whole drawer of them saved from broken lenses just for stuff like this.

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abby_scott3mo ago

Oh man, I had a similar thing happen with an old Minolta Rokkor rebuild. I figured I'd save a few bucks on those foam shims from some random eBay seller, and yeah, they just squished flat like a pancake under the ring. The whole lens flopped around after a day of use and I had to redo everything. I swear those old Perma-Cel shims are made from compressed unicorn hair or something, they just don't budge. I ended up having to order a vintage parts lot just to scavenge a few clean ones for future projects. It's a pain but at least you know what you're getting with the old stuff.

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