Based on all the testing that Silverfox1 is doing with his 70-200 II lens, his TCs and one of my TCs, I am coming to a conclusion about the near future. Perhaps even a logical conclusion. I'll bet that once again Canon has made a change in the communications between lens, TC and body on the 70-200 II and the III long lenses about to hit the shelves. Thus making 3rd party products not as desirable as they will not have all the features you want. Again, time for Sigma, Kenko and others to play ketchup. Didn't Kenko just come out with a new improved TC that didn't work right and needed a quick update? Only the new III TCs will work properly with the new long lenses, perhaps. After all what is a $500 TC when you just spent $10K on a lens? It is all relative afterall. The Leica R APO TC was list price over $2K and they still get almost $1K used. A dedicated TC is a big deal and worth extra money. All I am saying is that if you are getting one of the new long lenses, better throw a little more money into the budget for the new TC at the same time. Time will tell.
