Quote Originally Posted by _MD_
From what I've been able to gather, a 70-200 lens is an equivalent of 10x magnification.

Actually, on your 7D, it's the equivalent of 2.2X - 6.4X magnification (WRT the actual angle of view, not the viewfinder.)


Quote Originally Posted by _MD_
So I've looked at a bigger focal length lens such as Sigma 150-500 (Sigma also has 50-500), but most of the reviews say that the picture quality is not that great. So perhaps it will make sense to get a canon 70-200 f/2.8 on top of a canon 2x extender to achieve the maximum magnification?

The 70-200 f/2.8+2X TC looks better than the 50-500, but that's not saying much. The 150-500 is better, though.


Personally, I suggest the Canon 100-400. As far as telezooms go, it's very good.