I just returned from a few days vacation and intended on practicing what I've learned from these forums. Well, nothing kills that faster than a primary lens that doesn't want to work properly (and horrible lighting conditions). I have the 17-85 IS USM as my primary walkround lens. When I tried to use it the past few days, the autofocus would basically fail to work towards the longer end of the lens. At ~85mm, the autofocus would 'hunt' and never settle on something to focus on. The mid-focal range would focus, but the results were terrible. At the wide end of the lens, the autofocus seemed to be working fine. I thought at first that it might be the horrible overcast I was trying to shoot in, but I tested the lens again the next day under more ideal conditions with the same results. Here are a few examples.
 | HTTP response: 404 | MIME changed to 'image/png' | Byte size: ZERO |
This was at 56mm with autofocus. Exif should be intact.
| HTTP response: 404 | MIME changed to 'image/png' | Byte size: ZERO |
Also at 56mm, but with manual focus. Still not perfect, but I need the dioptic eyepiece or to wear my contacts on a more regular basis.
| HTTP response: 404 | MIME changed to 'image/png' | Byte size: ZERO |
68mm with autofocus.
| HTTP response: 404 | MIME changed to 'image/png' | Byte size: ZERO |
24mm with autofocus and looks fine.
So aside from the obvious lighting issues, does there appear to be an actual problem with the lens? I purchased the lens from a member here back in May and haven't really had any problems with it until now. The lens has not been dropped or abused by me in any way. I need to also note that the autofocus issue occurs with the IS on and off. Thanks!
