What to look for when buying used lenses

I'm thinking about going to look at a used canon EF 28-105mm f/3.5-4.5 II USM lens. Was wondering what are some for things I should be looking out for and is there a certain F stops I should test shoot at?


Thanks in advance, any tips or advice is greatly appreciated.

First off, what will you be shooting?
And second, what is your budget?

I make sure the glass is clean and scratch free. Maybe bring along a cleaning cloth in case there is a questionable mark on it. Next I put the lens on the body, go to Aperture priority. While pressing the DOF preview button I scroll through the different apertures and see if the aperture closes/opens while I am doing that. Take a couple of pictures. Make sure the lens focuses properly. Try this at different distances. Make sure the zoom ring works smoothly. Take a few pictures at different focal lengths. Then take a few at different apertures. Usually f/8 gives you the sharpest image.

Make sure the body is in good condition. Any dents could spell disaster. And if the price it too low there might be a reason why.

Hope that helps.

1. Buy from a POTN member.
2. Check the member's reputation on the Feedback thread (or ask the seller for links to their feedback)
3. I also check length of membership on the forum and number of posts.
Then I don't really have to worry about the lens itself as long as the member states that it is in great condition and has no problems.
Just a suggestion.

Don't get too upset if the lens has a scratch, either. A small scratch on the lens shouldn't affect quality at all as far as it's on the front element (the rear is a whole different story). The closer it is to the edge of the lens the less likely it is to have any impact whatsoever; if it's closer to the center it may result in higher probability of flare or lower contrast under certain conditions - but not always. This is based on personal experience - I have an old 28-90 that's been scratched in few places (literally thrown around by children) yet the photos it produces show absolutely no indication of any scratches. Some of them are probably 3-4 mm long. And the lenses with small scratches typically cost less. I would ask the seller to take several photographs with that lens in different lighting conditions and send them to you unedited . I would not buy from eBay, unless the member has a stellar reputation.