Originally posted by luftfluss I hope you get a chance to post some pics with the 400 DO II + 2x TC.
I got the EF2.0x III converter today. No birding yet, but a test shot. Coming from the DA560 + 1.4TC, this was going to be an important one, because the Canon 400DOII + EF2.0x at 800mm f8 is going to take the place of DA560 + 1.4TC at 784mm f8. For wading and perched songbirds, it has been an important combination of focal length and aperture for me. A 2.0TC is not generally part of a serious birding kit, only for the special shots, but I took a gamble that it would turn out right with the Canon EF2.0x III, which is regarded (with Sony's 2.0TC) as the best 2.0TC around, and would be at least as good as the 1.4TC on the DA560.
Here is a test shot on the 7DII at 2000 iso. I am pleasantly surprised to see no CA, either lateral or longitudinal, whatsoever in testing with the 400DOII + EF2.0x III, which was a bit of a problem with the DA560 + 1.4TC (mostly longitudinal, so impossible to clean up), and feel that it passes the critical detail test. Also, auto focus is still fast, responsive and mostly spot-on.
On the Sony A7rII, sharpness is even better, but auto focus is clearly not native, with quite a bit of travelling through the focus range, needing to set the limiter on the lens, and aid with manual forcus. Once in the region, it snaps into spot-on focus immediately.
Finally, the very, very good IS in the 400DOII really comes to aid handholding 800mm, making it almost cheatingly easy compared to the DA560+1.4TC, and the 7DII seems to get better at iso 800 to iso 2000 compared to the K3II, whereas the K3II is clearly better at iso 100- iso 200, and a tie inbetween. What the 7DII does very well, is hold colors at higher iso settings, where the K3 washes out above iso 1600.
Chris