Poll: Are focusing issues enough to merit returning a used Sigma lens?

So, I just sold a Sigma 24-70mm f/2.8 on eBay, and I was honest in my description. I said that I'd tested it out on both an XSi and a 5d2, and it focused pretty accurately on both, but at 60-70mm in low light, it was slightly hit-and-miss. In my opinion, that's to be expected. However, my Sigmalux performs differently on my 5d2 (+6 MA required) than it did on my 40D (perfect), so I worry that the lens I sold may have issues on the buyer's camera even though it was OK on mine. So now I'm playing the waiting game and crossing my fingers that everything's going to turn out well!

So, just out of curiosity, I want to see what you all think. Given an honest description of a lens as focusing well, is front/back-focusing a valid reason for returning a used Sigma to the seller?

how old of a lens? let the buyer send it in to sigma for calibration. Lens issues w/ his camera may be indicative of problems other than the lens. As long as it worked for you and your description is good, you've done your due diligence.

I don't know how old it is (I bought it used) but it's most certainly not covered by warranty. So any calibration would have to be paid for. Anyway, there are no problems YET, and frankly there shouldn't be, but I've still got those fingers crossed. I think perhaps we all worry a bit too much about Sigma lenses.

If you say the lens focuses well and I get it and it does not focus well, I'd expect to be able to return it for refund.

That said, I think part of the problem with all the web hype about Sigma is that mentally we are all looking for any missed focus at all. It is automatically "cause it's a Sigma" rather than user error, where if it was a Canon lens it might be the other way around.

tkbslc wrote in post #10844637
If you say the lens focuses well and I get it and it does not focus well, I'd expect to be able to return it for refund.

That said, I think part of the problem with all the web hype about Sigma is that mentally we are all looking for any missed focus at all. It is automatically "cause it's a Sigma" rather than user error, where if it was a Canon lens it might be the other way around.

Well, it's worth noting that I said that the lens focuses well on my camera. What I didn't write and probably should have is "I can't guarantee that it'll focus well on yours." I personally would still buy the lens, given that I have MA, if I saw that...but I'd consider that fair warning to anyone else.

I think you're right, at least as far as the two main culprits (the 30 and 50 1.4s) go. When I first got my Sigmalux (I had a 40d at the time), I was definitely looking for focus issues, and I found them. However, once I actually put the thing on a tripod and eliminated the "swaying photographer" effect, I found that it was simply a matter of the DoF being so damned thin that it was tough to nail focus. That being said, it DOES front-focus on my 5d2.