Roger N. Clark (change username to rnclark) wrote:
John Sheehy wrote:
I don't even like the AF of the 100-400 without a TC; I can't imagine
relying on it *with* a TC.

Some additional notes:
The 100-400 has no sealed rear end, so as you zoom the lens,
it pumps air into and out of the lens and camera, and
along with it, dust. I have a 100-400, and do not
like it with digital because of the dust factor.

Next, some copies of the 100-400 are not sharp. Mine is not
and produces soft images at 400. This has been noted by pro
bird photographer Art Morris in his newsletters too.
So if you want on, be sure to test the specific lens you will
buy.

If buying a new lens for wildlife, I would recommend
the 300 f/4 L IS or 400 f/5.6 L (no IS) over the 100-400.
Zoom is nice, but not at the expense of performance,
including AF speed, and sharpness.

I would like to add:

Canons 70-200 f2.8 L IS lens coupled to Canons 2x telextender attached
to a 30D (or 20D) gives excellent results at F5.6 at an equivalent
640mm; keeping the use of Modes 1 and 2 IS. This setup is what I use
for wildlife photos; still retaining the basic 70-200 for conventional
use.






Snip