I may have the wrong 2.8. The 70-200 f/2.8L IS II is sharper than the 70-200 f/4L IS. There are other versions of the lenses and I've lost track of which ones we're doing here, but the ones I mentioned, the 2.8 is far superior.
well maybe when you do shots of testcharts.. i doubt you can show me real life pictures where the difference is visible.
Now that the sun has come out for the first time this summer I better take advantage of it and go shoot some stuff. Ah, not even f2.8 can rescue a Scottish summer....
the main advantage of the f4 is weight.
i shoot landscapes with my 70-200 f4 most of the time (means hiking and travelling)
i rarely ever want to use the 70-200 lens at something faster then f5.6.
when i want to do portraits or something with a narrow DOF i use my fast prime lenses (85mm f1.2 or 135 f2).
70-200 f4 + 85mm f1.2 = 1785g in my kata backpack
70-200 f2.8 II + 85mm f1.2 = 2515g in my kata backpack
that´s why i have the 70-200mm f4 and not the f2.8.
it´s lightweight and fits my needs... your mileage may vary.
the 70-200 f2.8 II is sure a fantastic allrounder.
and the corner sharpness is impressive.