Lens test?

Is there a certain protocol to follow when buying a used lens to make sure it is functioning properly? I've bought several items off of craigslist without issue, but I am hesitant to purchase a quality lens due to the dollar investment you have to make.

In other words, would a visual inspection and firing a couple pictures with a lens be enough to warrant a purchase? I'm looking at a 24-105L lens for about $700. I'd be very unhappy if I got scammed.

Opinions and advice are greatly appreciated!

There are many ways to test a lens, and it often also depends on experience.

Here is a page with links to get you going:
http://www.sciencebudd​ies.org …hoto_p001.shtml​?from=Home

Personally, I'd do a few quick shootouts directed at a brick wall, parallel to it, and check if the resolution falls of equally towards the edges and corners, and I'll do that at different apertures (and FLs of course). I'll also check AF by aiming at the edge of a brick in the same wall, but at 45 degrees, again at different FLS.

I'd also make a few real life type shots, just to see how those look overall.

And before doing these tests, I'd make sure I know as much as possible about the lens in question, by studying reviews, and noting what to expect.

HTH, kind regards, Wim

Here's a nice article on the subject:

http://www.lensrentals​.com …010/11/how-to-test-a-lens

You probably won't be scammed.