Hello, wondering if anyone has seen an issue similar to this. My EF 28-135 has shown some difficulty focusing on my 5D (original). I've only owned the lens for a few months and didn't notice this issue earlier, but seems to becoming more frequent. Then lens basically will occasionally not focus on a point that seems to have plenty of contrast - no other lens would even hesitate to focus on the scenes I'm describing: outdoors, plenty of light and contrast at the focus point, only using center point focus, etc. If I recompose slightly, or change the focal length slightly, it will usually focus then I can shoot. Seems to happen throughout the zoom range, but probably more common at the long end. I haven't tested it rigorously yet. It hasn't rendered the lens useless, but it is getting a bit annoying.

I've never seen this on any other lens on my 5D. I haven't tried the lens on my 40D yet to see if I can get it to do the same thing there - that would let me see if it's a lens problem or a problem specific to the 5D/lens combo.

Anyway, any advice is welcome. Thanks!