> I've been interested in the Olympus/Zuiko 1.4X teleconverter, but they tend
> to be horribly expensive. I looked into the Tamron 140F (there is an
> affordable one on evilBay), but that one is intended to work only with
> primary (fixed) lenses.
While I don't know about other 1.4x teleconverters, the Zuiko
protrudes quite extensively into the attached lens. Olympus was wise
to put the guards in place on unmatched lenses to prevent optical
impact. The only thing I can think of is that the Zuiko 1.4x
teleconverter is overly happy.
As to performance, it does magnify any flaws in the primary lens. With
the 300/4.5, it performs pretty well on the A7 II, but is quite
difficult on the Four-Thirds cameras. I believe the optical stack in
front of the sensor is contributing to the problem. The thickness and
makeup of the sensor stack in the Sony (as well as the Canon 6D)
appear to be better matched for this lens combination.
Themed Olympus Photo Exhibition: http://www.tope.nl/