Upload & Sell: On
Well, a few months ago, I bought my 500/4IS locally and turned out it has mold. I decided to keep that lens and use it until it dies. It still produces sharp results but I just don't know how long.
Now, I just bought a used 100-400L in "mint condition" and the focus won't work right. It will attempt to focus, but the focus confirm light blinks...Sometimes it confirms, I'd say about 50% of the time. When it does, the lens seems plenty sharp. The lens almost locks onto the target but goes up and down up and down on the focus scale, almost like I was in servo mode (I am not).
I've cleaned the contacts, and the results are the same. I sent the lens to Canon and they said the USM works just fine. I've tried the lens on 3 cameras with the same results. I would assume the USM unit is defective, but Canon says no.
Anyone have a focus problem like this before?