>>2845911I'm not him, but I can vouch for Canon's 100mm f/2.8 Macro IS L lens. (Pic related, btw)
I know - why a macro lens? But this thing is just so DAMN LIGHT. Focus speed was never an issue, it's snappy as hell.
If weight (and price!) isn't an issue, you should look for a 70-200 2.8, but honestly I find that in these situations weight is hugely important. You can balance that 100 all day, while the 70-200 can get in the way, if you're in the crowd. Plus, Canon's 70-200 2.8 IS II is so good compared to the others that you will eventually regret not going all the way, if you pick up one of the cheaper ones.
I'd look for an used one, and if you value speed over IS, there's the forgotten one - Canon's 100mm f/2 lens.
On a 7d, it becomes a 160mm which is fairly long but should help with bigger stages.
If you're not planning on moving to FF soon or you're ok with reselling the lens for 30-40% less later on, Sigma just released its 50-100 f/1.8 crop lens.
