Last night I received from B&H a Kenko Teleplus PRO 300 DGX 1.4x AF Teleconverter for my 70-200 f/4 IS. Since I have a 70D I decided to check if a auto-focus micro-adjustment was needed. The 70D allows two adjustments, separately for the wide end and for the long end. Started the Dot-Tune procedure with the long end - almost dead on, no adjustment needed. Tried the short end - and it went beyond the scale.
The Dot-Tune procedure looks for the points at which the lens gets out of the focus range, and recommends to use the middle point between the left and the right points. So on the right it was -6. On the left it went to -20 (the extreme) and still was showing as "in-focus". I decided to set it at -13, in the middle between -6 and -20, but does anybody think that so much adjustment is ok for the wide end? Maybe it is worth sending the converter back for a replacement?
Any comment?
BTW, I do like the sharpness of the 70-200 with this teleconverter!
