Canon 800mm f/5.6L IS

Canon’s newest, longest telephoto lens. It’s lighter than the Canon 600 f4 IS by a pound although a bit longer. Early reports indicate that it’s every bit as sharp as the other Canon supertelephoto lenses, and the IS provides a full 4 stops of image stabilization (which can be important in a lens this long, even when mounted on a tripod).

It is fully compatible with the 1.4X teleconverter, although it will only autofocus on 1D series cameras with an extender mounted. Autofocus is not guaranteed, even on 1D bodies with the 2X teleconverter, although some report that center point autofocus may work, at least in bright light.

Roger’s (uninformed) take: First, I haven’t shot with this enough to have any worthwhile input, but I’m getting asked this all the time :
“Why the more expensive 800 f5.6 instead of a 600 f4 IS with a 1.4X converter”
1) Its a bit lighter and that might make a difference
2) The 800 f5.6 IS should be a bit sharper than the 600f4 with 1.4X. A bit.
3) 1600 mm with a 2X, although you have to manually focus.
4) That’s really all I can think of, but there’s got to be something I’m missing.