I'm fairly new to photography, but already got myself a Canon 7D with a 17-55 f/2.8 IS USM lens.


I'm on the market to get a good zoom lens, but I'm contemplating as to what brand, focal length, aperture, etc...





After some research I see that the most popular lens (in terms of build/picture quality) is Canon 70-200 f/2.8. For me, price isn't a big concern, but what I'm looking for in a lens, is a magnification level (and quality of the resulting picture too of course!) as well as versatility - it has to be a zoom lens and not a fixed focal length. Take for instance binoculars or bird-watching scopes - those lenses can magnify an object 20, 40, 60 times... From what I've been able to gather, a 70-200 lens is an equivalent of 10x magnification. 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? Please advise.





Thanks