Everyone else already answered your questions very well. The only thing that I would add is to encourage you to consider the Sigma 50mm f/1.4. It's another $150 or so, but almost everything about it is much better than the Canon 50mm f/1.4: contrast, resolution, bokeh, manual focus, etc. The only downside is that Sigma's QA is often not very good, and some buyers have gotten lenses that had to be returned. But then again, Canon's 50mm f/1.4 has poor build quality as well: one of (if not the most) highest repair rates of all Canon lenses. Whatever you end up with I'm sure you'll love it.