I am still a ameture but studying a two year course in Photography. About 1/4 of the way in to give a idea of my present level. I shoot with a Canon 7D and found that a lot of weaknesses of full frame lens are strongly deminished on crop sensor bodies. Plus add focal lenghts and I can upgrade later to a full frame body when I'm ready, ( the logic behind all my lens choices ).

I currently shoot with a Sigma 17-50 a crop sensor lens, a Sigma 70-200 EX DG APO II and this lens both full frame lenses. Although the the 17-50 might be described as a half stop more sharper in some instances but not all. This lens the Canon 24-105 is so much more amazing at it's color output by far!!

I love the quality if this lens and the functionality, plus the pictures i capture on my 7D with this lens look superior in color and composition to any other lens I have tried. Although the Sigma 17-50 is technically sharper then most lens costing much more thier color output doesn't compare. To Canon "L" Glass!

This lens has seals to help with moister and dust plus feels far superior to any thing else I have used todate. And it's build qualitiy I can a tests for first hand since I drop this lens mounted on my 7D with a battery pack and two batteries. The camera landed 4.5 feet down on carpet no padding on the edge of the barrel were the filter threads. Luckily I had a Hoya filter UV and it shatterd, But to my dismay I only found a very slight bend on the edge of the barrel where the lens landed and threaded a new filter with out any problem plus haven't found any other issues with the lens except a hair more play in the barrel when fully extended. " THIS LENS WON ME OVER FOR LIFE WHEN IT COMES TO L GLASS " (Posted on 2/26/11)