Please stop hosing down focus assemblies with contact cleaner, it's quietly eating the coatings

Ryan Gibson · 2026-09-17T01:25:06.114052+00:00

I keep seeing this in threads and in my own repair queue. Last month alone I had two Canon FD 50mm f/1.4 lenses come in from guys who sprayed the focus helicals and aperture blades down with generic contact cleaner to free up the grease, and both came back to me with fogged elements and a nasty film on the inner surfaces. Contact cleaner is great for electrical contacts, but it strips lubricant and can leave residue that attacks the coating on glass and the cement in older optics. I've been at this bench since 2011 and I can count on one hand the number of times a solvent spray actually fixed a stiff focus ring without causing a follow up problem. The right move is a full teardown, clean the helical with naphtha on a swab, and relube with a proper grease like Helimax. It's slower, sure, but it saves the customer's lens instead of wrecking it. If you've been doing the spray shortcut and getting away with it, what are you seeing on the glass a few months later?

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Please stop hosing down focus assemblies with contact cleaner, it's quietly eating the coatings | Camera Repairers - Discusd