I sent an email to Tamron asking if the TC and the 70-200 f2.8. Here is the response I received:
We do not recommend the use of teleconverters with digital lenses/cameras, as you may experience image quality or auto focus issues. For more information, please see this service update:
Tamron; Digital Camera Lens (DSLR), Security CCTV Lenses
If you have any other questions, please don't hesitate to contact me!
Regards,
Customer Service
Tamron USA, Inc.
10 Austin Blvd.
Commack, NY 11725
631-858-8400
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I might be selling my TC and try to find a lens/TC that is compatible. I like that 70-200mm range.
Any suggestions? Pentax? Sigma?