What to look for when inspecting used lens...

All,
My last used lens purchase question - I hope. So I'm purchasing used lens locally via Craigslist. The sale is pending my inspection of the lens (24-105L).
It's listed as mint condition and I've seen a few pics that look reasonably good.
Here's my question... I'm not an expert on what makes a great copy of a lens. When I inspect the lens (yes, I'll bring my camera), what would you suggest I look for to ensure I'm getting a good copy. Obviously I'll take some pics, but not sure of the best way to review the lens. I know the simple answer is... "take some pics and if it looks good, then go with it". I've only ever shot a 28-135 on my camera, so I'm just assuming the 24-105L will "look good". But that doesn't necessarily answer if its a good copy or if there's any issues with it. Please, give me a list of what I should be inspecting before deciding the copy is "mint".
Thx.

I usually try to establish if the seller is the original owner by asking to see their original receipt. My theory is that if the seller is the original owner the lens may have been better cared for.

I generally shy away from lens resellers - YMMV

Look at the outside condition, like make sure there are no scratches on lens or body. Zoom in and out and turn the focusing ring to insure smoothness. Look through the lens wide open with a flashlight to make sure there is no mold or dust inside lens.

Take Care,
Cheers, Patrick

Saint728 wrote in post #8616073
Look through the lens wide open with a flashlight to make sure there is no mold or dust inside lens.

If you look with a flash light, almost any lens is going to have some dust inside.

Nothing to worry about.

Take your time and don't feel rushed. It's your money. The seller should leave you alone and give you a wide berth for testing, but do respect that it's still his/her lens until you pay for it, so handle it with care. If you really are extra dilligent, bring a printed test chart or a ruler with you and test shoot it to look for back/front focus issues. If you are super extra dilligent, bring a laptop and pixel peep 100% crop instead of relying on the camera LCD.

From the seller POV: I've sold quite a few lenses on CL. None of them was lower than $800. I want the buyer to have plenty of time and comfort to inspect and test drive the lens. I choose to meet at library or book store for a neutral zone with plenty of sitting area and tables.

Regarding the comment above on reseller - I don't see why a second/third/fourth owner wouldn't want to be just as careful with the lens as the first owner, having bought it used and knowing he/she can sell it at a much better price if the lens has been properly taken care of.

Bring some lens cleaning tissue and blower with you to make sure there is no scratch. check the focus ring.

Do some homework before to see how sharp the lens should be, and understand if there is any limitation. For example, it is well know the 70-200 is soft at minimum focus distance. I usually use this web site.

http://the-digital-picture.com …ample-Crops.aspx?Lens=355

Then, take pictures at all focal length to make sure it focus correctly, especially at wide open and long focal length where the DOF is very shallow. Bring a lap top and zoom in 100% to check. If I am buying something expensive, I will bring a tripod, test chart or some of my son's wooden block to do a focus test.

It is also important to stop yourself from buying it if you don't feel comfortable. It is human nature to get it since you spent alot of effort already, and don't want to leave empty handed. This is a lesson I learn .. don't feel bad if you don't buy it. Otherwise, you will regret.

Check that the zoom ring is smooth (or at least not rough, the ring sticking at one end or the other is normal) and there isn't an abnormal amount of zoom creep. Check that there's no mold in the glass - dust is fine, scratches on the front element are fine and can be used as a bargaining tool. Anything other than dust behind the rear element is a bad thing.

Minor nicks and scrapes are nothing to worry about. Lenses are tools and get used. If there are not-so-minor nicks, ask when the last time the lens was serviced. A professional photographer might be more careless with their equipment in the field, but they're more likely to get it regularly serviced and (generally) know how to store it.

Bring a laptop or something so you can load your test shots. You won't be able to make an accurate judgment on whether it's a great copy or not, unless you've had several copies of that lens before, but you'll know if there's something wrong.

Maybe bring someone with you that has good luck buying used lenses.

gte357s wrote in post #8616462
Bring some lens cleaning tissue and blower with you to make sure there is no scratch.

If I were the seller, I wouldn't let you clean it. I would let you use the blower and brush (which I always bring to a transaction), but no, no, no wiping. Remember, you don't own it. You scratch it, you buy it.

L_F_L wrote in post #8617548
If I were the seller, I wouldn't let you clean it. I would let you use the blower and brush (which I always bring to a transaction), but no, no, no wiping. Remember, you don't own it. You scratch it, you buy it.

Yes, of course need to ask the seller, or the seller clean it himself. There may be markings that can't tell whether it is a scratch or not. So, I will always bring it with me, and it doesn't hurt to ask. If seller agrees to wipe it, and prove that it is not a scratch, that's great. If not, then don't buy it if there is any doubt.

Check the date code. Early versions of the 24-105L had bad flare issues that required a repair by Canon. Make sure that the lens you're considering has a UU or later date code. Date code UT and earlier should be considered suspect if the owner cannot prove if the repairs had been performed by Canon.

can someone define zoom creep?

Is this when a lens is held verticle to the floor and it extends on it's own?
Is this ok and normal?

Thanks

Isn't this a lot of time and bother just to save a few pennies using Craigslist? Buy from a reputable dealer with a return policy.

gasrocks wrote in post #8642923
Isn't this a lot of time and bother just to save a few pennies using Craigslist? Buy from a reputable dealer with a return policy.

Not at all

I picked up my mint 100-400L with all accessories for $900 bucks off CL and saved quite a bit more than just a few pennies

There are deals out there to be had and in most cases, if a lens has a problem serious enough to cause flawed images, it will most likely turn up during the first few minutes of initial testing

Honestly, the way things have gone for me in the past, I doubt I'll ever buy a new lens uness I'm not able to find one used (or hit the lotto lol)

Nevermind, I did some research and get the picture now...sorry for a newbie question.