On Sat, 8 Sep 2007 23:18:34 +0200, Wolfgang Weisselberg
wrote:

King Sardon wrote:
My 17-55mm f2.8 IS lens was not autofocusing well with my Rebel XT
body.
My other lenses autofocus well and dependably with the Rebel, but not
the 17-55mm f2.8 IS.

I sent the lens in to Canon for them to fix the autofocus under
warranty. But they returned the lens saying that it was working fine.

Always send in lens AND body.
You have now experienced _why_.

So I tried the lens out on a friend's 20D, and sure enough, the lens
works fine with the 20D... but not with my Rebel XT. The lens is still
in its warranty period, but the Rebel is not. Not sure what to do now.

Send in lens and body this time. Add shots where you demonstrate
the misfocussing.

Does anyone else have this problem with the 17-55mm f2.8 IS lens on
the Rebel? I'm wondering if it is a design fault or a sample issue.

Most certainly it is not a design fault, or RichA would have been
jabbering and drooling on it for years, the net would be full of
it ...

My guess is that the offset from true focus in your Rebel for
this lens is scrambled for some reason. Which is why you send
in the lens and the body, and images showing the problem.

-Wolfgang

Thanks for your advice, which I followed early this morning. The store
where I bought the body has a very sagacious owner who somehow noticed
what was going on while I was discussing the problem (again) with one
of his sales guys. He came up, declared "this is a back focus
problem", "it's not the lens, it's not the body, it's the interaction
between them", "happens all the time, including with $10k cameras",
etc.

So body and lens are off to Canon for repairs under warranty.

KS