I am thinking of getting either the f/2.8 IS or the f/4.0 IS, and I would like to especially hear from former f/4.0 IS owners.
So far, I have been leaning toward the f/4.0 IS for the following reasons:
1) Superior optics - prime like sharpness
2) Released in 2006, with 3rd gen Image Stabilization
3) For outdoor use, no issues w/shutter speed - I'm willing to shoot my 1DsMkII at double ISO.
4) More likely that its image will look sharper @400mm (w/2x TC)
However the f/2.8 is still tempting because:
1) Shallower DoF
2) Faster and possibly more accurate focusing, due to 2x light being delivered to sensors.
3) Again, better focusing due to my camera's f/2.8-or-faster set of sensors
4) Love the "big gun" look, with the petal shape hood!
I know there are several of you who SOLD your f/4.0 IS to get f/2.8 IS, and I also know who have gone the opposite direction. Do you feel that you have lost sharpness in your images having done so? Do you feel that f/2.8 focuses faster? Was f/4.0 really that limiting, over f/2.8 (in terms of shutter speed)?
As you can tell, the price and weight aren't issues for me. Also, I am 95% positive that I'll be shooting mostly shooting outdoors with this lens. I am mostly shooting my family.
I would appreciate your thoughts! Thanks.