My 28-200 EF doesn't want to focus longer than 170mm!!!

Anybody find this to be true? Most of the time, with few exceptions my copy of this lens will not focus lock at focal lengths beyond about 160-170 mm according to the indications on the barrel.

It hunts for about 3-5 seconds then quits,usually out of focus. At shorter focal lengths it is fairly quick and quiet.

I know this is an "el-cheapo" for Canon, but I would have expected it to function at full length.

I do not have this lens, but perhaps at 200mm the aperture is too small to get enough light for a decent focus for your camera? I figure this is a variable-aperture lens with aperture varying on the current focal length. Did you try shooting outdoors in daylight against some high-contrast subject to see if you have this problem?

I see what you're saying about the lens aperture, but I've never had any other lens do that at F5.6.

I'll test it again this afternoon in the bright sunlight. I'm using it on a 50D that I've never had an issue with.

It worked only slighty in very bright light against high contrast images.

Have you tried to force ISO up?

AsiaStudio wrote in post #9478226
Have you tried to force ISO up?

Thats not going to help the focus

But honestly, i cant say i've heard of this happening before..even with say, the Sigma 150-500 and that which are f/6.3 at the long end...

Also as the OP stated, if it was a camera body issue he'd have problems with other lenses which have a max aperture of f/5.6...

sounds defective, if you just got it exchange it