I've used one... unless you are REALLY REALLY picky, you wont notice the difference between the sigma 70-200 2.8 and the Canon 70-200 2.8L...
The canon one is much more reliable in terms of focus accuracy, and just that hint sharper at 2.8, a little more contrasty depending on the conditions... but overall, its much of a muchness....
Stopped to F/4~F/8 its almost impossible to know the difference between them.
|