I don't have a TC so I don't know what the conversion would be. the 100-400 is a little slow in the dark but not in the sun. And it's fine in moderate light. I LOVE it. But it's not speedy
(but neither is the 5D, which is what I use it with). I shot whales from a great distance on a very cloudy/overcast day and had no prob. catching the shots.Thanks permagrin..
Right now my list of lens to buy are:
70-200L 2.8 IS
100-400L
and a 24-70 2.8L to replace my 17-85
**sighs and fills out another job application**





