Sticky Focus

Picked up a 50mm MkI today (the original, metal mount) at an antique store, attached to an EOS 750 (didn't know stuff from 1988 was considered antique, but I digress).

Anyway, everything works great, except when you first go to focus (manually of with AF) if the lens has been sitting for a bit (a couple of hours) - it focus is 'stuck' wherever it was left after last use. It frees right up with just a hair more torque then normally in MF, but in AF, it won't budge. You have to switch to MF, free it up, then everything it fine. But once you leave it alone for an undetermined length of time, it sticks again.

Anyone have any ideas what's causing it, or if it can be remedied? It focuses fast and accurately, blades are dry, and everything seems normal otherwise.

So, are you saying you can get it to work in AF OK? Go with that. Probably not worth a repair bill.

Something is obviously gummed up. I personally don't buy used equipment for this precise reason. Bought a nice contax lens off ebay a couple years ago that was listed as mint, no oil on blades etc. aperture stuck after first shot. Are you sure here is no gummed up oil on the blades?

Gasrocks, yup,works perfectly, once you 'free' it up. The AF will work fine until you stop using it for some time frame which I haven't figured out yet as to how long. Used it for about two he's, no problem. Put it down, came back about three he's later, and it was stuck. Manually moved it, and it was fine again.

Frodge, not a speck of oil, and the body of the lens looks nearly new. New or used, I won't pass on a steal of a deal.

If they used an oil in the AF system, I could see it being gummed up from age, but they don't. Wonder if maybe there is a dust bunny in there.

If it was a great deal and you like the lens I say just live with it. Realize it will affect resale value. If used often enough, it may get better. I have seen many lenses do this after they sat unused for a long time. Gene