The following is a direct quote from the folks that found the problem. Tamron’sresponseis at the bottom.
i am a member of the german dslr-forum (
www.dslr-forum.de), which isprobably the biggest german speaking community regarding all DSLR-topics(not only Canon). We observed a phenomenon where the followings lenseswon’t use the outer cross-type sensors of EOS 40/50/60/7D cameras right.
The lenses that show this problem are (all Tamron):
- 17-50 f/2.8 VC
- 60 f/2 Macro
- 70-200 f/2.8
- 10-24 f/3.5-4.5
To get a bit more into the detail of the problem – on the 40/50/60Dcameras the outer cross-type sensors only work as line-type sensors. Tobe a bit more correct, they actually work in the same direction as theywould work on cams like the 30D or like the 400/450/500/550D. When itcomes to the 7D the outer sensors are also only working as line-typesensors (but it seems, that the EF 50 1.2L also has problems to use themcorrect).
The center cross-type sensor does work at least as a single-cross typesensor (infact we don’t now how to test if the center sensor is workingas a dual-cross-type sensor like it’s supposed to work with those f/2.8and better lenses).
Tamron seems to not know about this behaviour so far. Well – at least,they didn’t confirmed the problem and only said, that they willinvestigate this.
Maybe a small addition – the Tamron 17-50 VC uses the same lens-ID asthe EF 35-80 – maybe you’ll have the chance to check whether thisCanon-lens performs correctly or not.
The link to the thread is:
http://www.dslr-forum.de/showthread.php?t=732360
Tamron Europe’s Official Response
Dear Mr. S.,
we were able to reproduce the situation where the Tamron 17-50 VC (B005)and the Tamron 60 Macro (G005) won’t use the Canon EOS 50D cross-typesensors correctly.
We have given this information to Tamron in Japan and we are expect ananswer very soon.
Best regards
Tamron Europe GmbH