There are "refurbished" and then there are "used".
Refurbs are "technically" not new because they were previously sold to someone -- but they are returned to like-new condition and typically come with a factory warranty (at least they do if you buy them direct from the Canon store)
Used gear is simply "used" -- and will likely show signs of wear and tear depending on how heavily used they were and how well they were cared for. Heavily used lenses can have internal wear causes the focus mechanism to get a bit sloppy (gear backlash). There can also be internal dust or even fungus (which grows on the coatings of the glass.) For this reason, I'd be especially carefully when buying "used" gear.
If you're going to shop for "used" gear then check places have a good reputation and a grading system. KEH.com, B&H Photo, Adorama, etc. They'll grade and report the condition of the lens and the general opinion is that their grading system tends to be fairly strict (if they say there are no cosmetic scratche then there had better be NO cosmetic scratches (a tiny minor and hardly noticeable scratch would cause it to get bumped to the next category down.)) That means you tend to be able to believe the grade they gave it.
If you buy from eBay or Craigslist things become less certain. eBay is a bit better in that sellers are expected to accurately represent the condition of used goods and eBay offers some buyer protection. But the risk here is that you might encounter a dishonest seller and the more likely possibility is that the seller simply does not have the expertise to accurately evaluate the condition of the gear.
If you find gear at a garage sale you are, at least, standing there holding the gear in your own hands while you evaluate it. So if YOU know what to look for you might find a bargain (and usualy the prices are the best.)
Craigslilst is probably rock-bottom... it's basically a garage sale where you do not get to hold the gear and evaluate it nor do you get any type of buyer protection with the purchase. I would never buy from Craigslist unless the seller actually was local and agreed to meet somewhere so I could evaluate the condition of the lens myself.
Bring your camera body with you. You want to look for things such as:
- Obvious external signs of physical damage (dents, big scratches, etc.) Also do not forget to inspect the filter threads on the front of the lens. If the lens was dropped or hit on object at the front, those threads will often be dented such as it's no longer possible to thread on a filter -- even though the rest of the lens is fine.
- Remove the front and back caps and look at the elements within the lens for signs of fungus or internal contamination (dust, etc.)
- Rotate the focus ring a few times from end to end and "feel" how smooth it is. There should be some resistance but it should be other smooth with no grinding noises, it shoudl not jam, etc.
- Rotate the zoom ring and similarly test for smoothness, jamming, etc.
Attach it to your camera body and check that the auto-focus actually does work. Unfortuantely it's difficult to check for gear backlash without a focus test target and a tripod, but that would be something I would be interested in knowing. You can set a minimum depth of field, maximize the focal length, and focus on a target as near as possible (this minimizes the depth of field-- if the lens is missing focus it will hopefully be detected when you inspect the image.)
Tim Campbell
5D III, 5D IV, 60Da
