EF 35-350L and EF1.4XII or EF2.0XII

Hi,
I posted this question a few weeks ago on the T/C sticky but never got a reply...perhaps the thread's too old.

I have a 35-350L and am wondering why it cannot be used with the T/C's.
The rear end of the lens looks identical to my 70-200 f/2.8L.

None of this lists I see for lenses that can be used with the T/C's show this beast.

Bob

Because 10x zooms just don't give good IQ with teleconverters.

The lens is not a fast lens, and adding TCs will lose 1-2 stops of light - in most cases losing AF ability and certainly giving IQ a serious nose dive.

You could probably get a third party TC to fit no problem though. Kenko certainly would fit any Ef lens, I believe, if you are desperate to try.

Thanks guys.
I was under the impression that it was a "cannot be done" rather than "can be done but with less than clever results".
As far as speed goes, it's a f/3.5 so it outranks the F/4 L lenses which are mainly included in the compatiable lists.

It's f/3.5 but that's just at the 35mm end. At 350mm it's f/5.6
And if it's anything like the 28-300L, the rear element will run into the teleconverter at the wide end.