default wrote:
You will not be pleased with a 2x teleconvertor.

My Kenko Pro 1.4x works great. I use it with my 24-135 Tamron f/3.5-5.6
and Canon 70-200L f/4. I don't use it much with the Tamron, only when I
have room to bring one lens with me, but I believe it autofocuses at the
long end. The correct aperture doesn't get reported for the Tamron so
the camera thinks it's f/5.6.

Greg

--
"All my time I spent in heaven
Revelries of dance and wine
Waking to the sound of laughter
Up I'd rise and kiss the sky" - The Mekons