zoom

Optically, you can't really do that much better than the f/1.8 - strong contrast, good color rendition, and very sharp even when shooting wide open. I bought this lens and it lived on my camera for several months and was the default piece of glass that I reached for when the quality of the shot "really mattered."

But, honestly, it's built about as solid as a toy prize in a box of Cracker Jack. After a few months of use - use, not abuse - the lens literally came apart, the front barrel separated from the mount. The bad news was that the lens was completely shot - it was in pieces, after all - the good news was that it had been cheap, so my pocketbook was able to stand the cost of replacement.

I replaced the lens with it's older brother, a used version of the Mark I - much more solid, and which gives equal optical quality even used. It's a shame that the body and housing on new version of this lens is so shamefully cheap, because the glass is very nice. But I can't recommend it, unless you either a) don't do that much shooting, or b) don't mind replacing the lens on a fairly regular basis.

My suggestion is to either cough up the money for Canon's 50mm f/1.4 - gains you a half a stop and is built to pro-quality standards - or pick up the older version of the f/1.8 on the used market. Either option will likely end up being cheaper in the long run.