Rudy's findings and amazement were nothing more than rational observations from a medical doctor who was, -by exception-, amazed and even a little nervous while talking to me on the phone about this, some kind of exitement which is not usual for him...
About the 70-200AF-S VRII and TC-20 E III (which I call "the magic combo") itself, here below you can read my user' observations, findings, impressions and thoughts : Please take into consideration that all comments, observations, findings and test pictures are from this combo on a Nikon D700 FX camera.
The VR on the 70-200 AF-S VRIII was reported by professional reviewers on different fora as exceptional, I can only confirm that. Taking a decent sharp shot handhold @ 200mm and 1/10 sec is possible with good technique.
In relation to this exceptional VR quality of the main lens, and to my astonishment, the TC-20 E III transmits this exceptional VR quality to this lens-TC combination. You can take decent sharp, contrasty pictures @ 400mm, wide open(F5.6) and a shutter speed of 1/30 to even 1/15 sec. See my samples here.
Sharpness this combo can deliver, even wide open(F5.6) and @ 400mm, is much better than my 80-400VR used to deliver, even though I was a big fan of this lens. Some samples here.
AF speed and accuracy of this combo is amazing fast and accurate, but the 200-400 F4 on its own is still focusing much faster, next to the advantage having F4 wide open against F5.6 of the magic combo. Samples of the AF speed and accuracy, also in continuous AF you can find here and here.
Here you find a summing up of the separate topics of my findings about the AF.
70-200VRII+TCIII AF test-part 1-Easy targets

70-200VRII+TCIII AF test-part 2: Continu AF on moving target

70-200VRII+TCIII test-part 3: AF in low light and VR

70-200VRII+TCIII test-part 4: Continuous AF for moderate action
70-200VRII+TCIII test-part 5: Continuous AF for birds in flight.

Coming soon:
80-400VR vs 70-200VRII+ TC2.0 E III on D700
70-200VRII+ TC2.0 E III on D300, findings, thoughts and sample shots
[b]About CA and purple fringing: I see nothing suspicious until now, even though I didn't have the time to pixel-peep about this and I didn't take any high contrasty images like a brach of a tree agaist the backgound of a sunny sky yet... Some sample pictures with 100% crops of the details here.
About vignetting: Vignetting is extremely well controlled and barely visible wide open and much better about this than the VRII and Kenko pro 300 combo which I tested about a week ago...
About corner sharpness in the images this combo can deliver: This is ,-just like the original 70-200VRII-, nothing less than exceptional. You can find some samples here(for vignetting) and here(for corner sharpness).
My conclusion:
If your budget is limited (like mine, no joke, I depend on the goodwill and agreement of my lovely wife Rita...) this 70-200VRII + TC-20 E III is a good and cheaper all-in-one-alternative for having/buying several lenses like the the 70-200VRII, 80-400VR(or its successor) and the 200-400AF-S VR. It is not a replacement of the 200-400F4(which is focusing even much faster and tracking better), nor a replacement of the very probable upcoming 80-400 VR successor(which will very probably-, also focus faster and have a much more interesting "instant" focal range.)
In relation to all this an anecdote from my photography mate Rudy: While he isn't a real wildlife photographer and while the AF function doens't work on his 200-400 F4 in combination with the TC-20 E III, and last but not least because he finds the 200-400 F4 too heavy, he sells his 200-400 F4 AF-S VR...
Update(feb14th) and important notice: When doing this review I was clearly in the headline of this topic that it was about "70-200VRII+TC-20 E III on FX camera", while using this combo on a D300, the results I got are far inferior.
Our company buys most of its photographic equipment @ Audiophil, Aachen-Germany. Those people are extremely friendly, the sales people and the owner are photographers by education which means in this shop they know really what they are talking about. Prices are not the lowest you can find on the internet but moderate and very low if you take the advantages of buying there in consideration, and, last but not least, they speak German(of course) English, Dutch, and French....
My contact there is Mme Fadéla Hocini, an extremely friendly and charming lady with good knowledge about photographic equipment and, for me very important, she speaks French.
--------------------------------------------------------------------------------
PS If you would like to participate in this discussion you have to join this forum first. How to join this forum you can read here.
"Everybody is welcome on this forum, but not anonymous."
--------------------------------------------------------------------------------
... you have to do *right mouseclick* while pointing with the cursor on the red ImageDoesNotShowUp-sign and *"show image"- command to see the picture*. After that it shows up.Update: Underwhile this problem should be solved after transferring the pictures to a faster accessible server, but I let the notice here anyhown for in case...
