buying used lenses...help with what to look for?
 

I may be picking up a used lens tonight and since I have no experience with this, anything I should be looking for as a "red flag"?
I will bring my camera and make sure the obvious stuff works like the autofocus and zoom. I was also thinking of bringing my focus chart and snap a pic or two, then snap a few of the surrounding area.
Beyond that, anything else?

Lots of things, some not so easy to tell...

Look at the overall condition. Look at the front and rear elements to make sure there are no scratches or pitting. Work the aperture ring (if it has one) and ensure smooth movement. If it has an aperture ring, watch the aperture open and close through the lens while you work it to be sure it's doing it's job.

Look for any fungus or growth inside the lens or on the back element. Take a tripod and plate with you and do take some shots with it. Make sure the movement of the focus (and zoom if equipped) is smooth.

That should at least give you some basic idea of what you're buying.

thanks for the advice! Bummed that the guy never called back. Would have been the bargain of the century had the lens been as described, perfect condition. 28-300 Canon L (BH sells for $2400) guy wanted less than half! ARRRRRRGH!

Got a new 70-200 f/4L instead!