Paul, this link might help you. If you want a fast 50mm Lens the standard canon 50mm f1.8 is very good for the price. I've seen lots of favourable comment on this lens and because it's fixed focal length it has less elements than a zoom and hence it's sharper and has less chromatic abberation. The 50mm is quite refined because it was the workhorse lense for 35mm SLR's for years and makes a great portrait lens as well on a digital. (Equivalent to a 70mm on a 35 mm camera). Bear in mind that the lower the f number the shallower the depth of field (focus) is.
For reviews and testing have a look at this link.
http://www.bobatkins.com/photography...00dlenses.html and
http://www.bobatkins.com/photography...on_28_75c.html