As I think James Clerk Maxwell once said, 'if i have seen further it is because I stand on the back of giants'. I think Canon spent literally tens of millions developing the design and construction of these lenses. The 300mm F2.8L is considered to be one of the 'best' lenses ever built.
Here is it's MTF plot.
The fact that all the plotted lines are near 100% contrast means that the lens is as good at f2.8 as it is at F8! The lower dotted lines tell you it is not perfect and has slight astigmatism past about 15mm off axis. Here is how to read MTF charts.
http://www.luminous-landscape.com/tu...ding-mtf.shtml
http://www.luminous-landscape.com/tu...contrast.shtml
Bert