I have a Sigma 500mm f/4.5 lens. Just recently, my auto-focus does not seem to work. I know it is not the camera because I put it on my Canon 300mm f/4 IS lens and the auto focus works fine. Every once in awhile, the auto focus will start to work again. The battery is fully charged as well. While pushing down the shutter for focusing, the focus ring does not move at all. And yes, the lens is switched to AF.
Dan,
How old is the Sigma lens? Check if the firmware in this lens is compatible with your camera. Since you are using the Mark III, I suspect it is the lens.
Long back, when I used to use Sigma lenses, I faced this problem. I had a Sigma 300mm and the problem started when I bought the Canon EOS 30. The EOS 30 had latest software and the Sigma was not compatible. I first thought that the Canon Camera has the problem and got it checked. Then got the Sigma checked at the Sigma service centre. Then gave the Sigma lens to Canon Service centre and they told me that the sigma had got old software in it. So the Sigma had to be sent to Japan to get the latest stuff loaded. That day, I decided not to use any third party lenses.
So you get your Sigma checked. Most likely installing the latest software would solve the issue.
Cheers,
Sabyasachi
Dan,
When the lens originally stopped AF, was it cold? (I had that happen once.) When it started working again, had you cleaned the electrical contacts? If so, that might have been part of the "fix". Otherwise, the fact that AF started working again after you manually turned the focus ring might indicate a mechanical problem in the focus mechanism (worn or damaged parts, or something that had been knocked out of alignment by a shock). I suggest you run the focus all the way from end to end several times, both manually and auto (point it at blank sky so it can't focus and has to hunt), and watch for any misbehavior such as stickiness, pauses, or sudden jumps.
As an engineer, I hate it when something that seemed to be broken just starts working again for no apparent reason - I'd much rather it stayed broken until I can figure out why it wasn't working right. It leaves me wondering when it's going to misbehave again, and Murphy says it'll happen at the worst possible time (like 1000 miles from home with no alternate lens). Several years ago I had a different Sigma lens that abruptly stopped focusing (AF or MF), but it stayed broken. In that instance cleaning the contacts had no effect (though that's been the culprit a couple other times with different lenses). Sent the lens to Sigma for repair (under warranty), and never had any more trouble with it.
If you have any remaining concerns about your lens, I'd advise sending it to Sigma for a checkup, with a detailed explanation of its recent misbehavior.
Dan ...I had same problem plus others with my Sigma 50-500, Sigma replaced 5 lenses for me...always firmware or mechanical problems..using this lens on my Nikon D70.
My lens would get stuck at infinity and then I had to move it to get focus moving again (agrre with above, happened when cold)...Another lens would focus great between 0 - 100 then not aquire focus of anything further out..Sold it and also will stay away from 3rd party lenses...Paul
p.s. great lens when it was working though, for price.
Last edited by Paul Lagasi; 11-30-2008 at 04:53 PM.
I too have similar problems with the Sigma 400mm f5.6, it is an old lens and I had it re-chipped. It is thoroughly unreliable, sometimes it works sometimes it doesn't, then I got the dreaded error 99, since then I have only bought Canon lenses and have had no problems. It is a shame really because the lens was very good optically.
Sigma lens focusing problem
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