what kind of lens should i get for a canon t1i to acheive these kind of

[Candid Chris]

Your mega-pixels aren't the issue.
It appears that Julia has some nice glass and knows how to use it.
Have you tried the Canon EF 70-200 1:2.8 L ?

 

[Stéphanie]

photos at a concert? http://www.photoshelter.com/c/juliazavephotography

i have tried all different lenses. can someone please tell me the correct one to use?
by the way, i havent tried my new canon rebel t1i at a concert yet.

also, i sold my canon rebel xsi for the t1i. the xsi is 12.3 mp and the t1i is 15.1. will that make photos better too? thanks in advance 10 points!