Silverfox1 wrote in post #9259257
My next tele is going to be the 70-200 F4 IS USM since most folks claim very little degradation on image quality when it is fitted with either the Kenko 1.4 pro or the Canon extender.
What is your observation or knowledge with the F4 IS USM ?
No knowledge whatsoever with the f/4 IS. In general, I find that tc's work well in very good light with primes, usually stopped down a bit and when there's not a lot of cropping. There are exceptions of course, and the f/4 IS may very well be one of them. But I wouldn't know .
Nmura wrote in post #9259392
Combo is a 70-200, f2.8, with a 1.4x = 4.0. I read that the 2x tele is not that great. Did you mean the 1.4x or 2x tele or both not acceptable.
My experiences are with the 70-200 f/2.8 IS and the Sigma 1.4x TC. Because I had sold my Sigma 100-300 and needed a zoom for a softball game, I used the 7-2IS w/1.4x TC at f/5.6 on a sunny day. Recently I was asked to make prints from those photos and I realized just how limiting that combo is.
If you haven't looked into a Sigma 100-300 f/4 you might want to (Btw, I managed to buy mine back from it's second owner - great lens!)