I have read several positive reviews about the Canon 75-300mm USM III lens but I don't share other people's enthusiasm because it is not nearly as sharp as I would expect from a Canon lens.

Of course, compared to the Canon L Series lenses, this is an incredibly inexpensive item and, in its defence, I do find that my Canon EOS 50D, with it's jam-packed 15mp APS-C sensor, is very difficult to marry up with a lense to get the most out of it (unless you are prepared to spend thousands).

At the close end of the focal range, the picture is crisp and sharp but unfortunately this tails off quite noticeably as the lens is extended (as does the auto-focus accuracy) and I have even taken to focusing the lens manually when it is at full extent, using the camera's magnified live-view to ensure crisp results. It is also a little slow at the long end and, an anything but a sunny day, I have to compensate by boosting the ISO (which I am loathe to do).

On the plus side, the lens feels well-built but is not so heavy that it needs its own tripod mount. The auto-focus is fast and quiet, and the adjustment rings feel solid - and I have not noticed any "creeping" of the extendable section while the camera is being carried around. I also find that the camera and lens feel quite balanced together.

I have a feeling that this lens would be much better suited to a lower-resolution model (or a full-frame camera) than to the tiny pixels on my 50D - and, having reviewed a lot of photographic equipment, you could argue that I am much more fussy than the average man-in-the-street - but I would be tempted to look at the available alternatives before committing to buy.