Bests & Worsts Reviews from Amazon

This is the lens I leave on my camera for general purpose use. At non-macro focus distances, it is a very fast lens in a convenient short-telephoto length. The images are sharp out to the corners. This is one of those great Canon lenses that probably deserves an L-series rating but is available without the red stripe and exorbitant cost. Tested in an astrophotography context (point sources on black backgrounds - excellent for revealing aberration and coma), I have found that this lens is reasonably sharp at f/4 and completely sharp by f/5.6. For daylight terrestrial photography, the tiny aberrations caused by the wide-open f/2.8 aperture are hardy noticeable and by f/4 the images are exquisitely sharp. There is a lot of glass in this lens - it is heavy. I highly recommend buying the tripod collar as it allows you to attach the camera and lens to a tripod or ballhead with much better balance. Also, if you plan on using the macro functionality, keep in mind that the effective f-stop of the lens goes way up when you're focusing at very close range. At 15cm from the front surface, it performs as though it were an f/9. You'll either want a lot of light or a very steady subject and a good tripod (another reason to buy the hideously overpriced tripod collar).