Quote Originally Posted by neuroanatomist
IQ is usually worse with a TC than with a native lens, although it really seems to me that the EF 70-200mm f/2.8L IS II at 280mm f/4 rivals the 300mm f/4L!

In the center, maybe. But the prime looks far better to me in midframe and the corners. (As it had better... the day an L prime loses to a zoom + extender is the day I throw said L prime in the trash [] )