Photography - Teleconverters

In message ,
Mister_K wrote:

I am looking for opinions from teleconverter users ...

Minolta Maxxum APO 1.4x AF
Tamron Maxxum 1.4x AF
Sigma Maxxum EZ APO 1.4x AF
used with Sigma AF 400mm f5.6

and

Canon Extender 1.4xA
used with Canon FD 400mm f4.5

I would like to here some real life experiences with these or other
teleconverters.

I don't know any of these by name (I have the Canon 1.4x II and the
Tamron SP 2x (which is exactly the same TC as the Kenko Pro 300 2x), and
they both work great, as long as you use manual focusing, and the MTF of
the lens used is hugging the 1.0 mark. If the MTF is much less for the
aperture used, you are going to get emptier magnification.

IOW, teleconverters are ony useful with very sharp lenses. They are
most useful also on mediums with medium or lower resolution; if you use
a low-speed, high-res B&W film, you are probably better off taking the
shot without the converter, and just blowing it up more, without
sacrificing your photon budget to the needs of the converter. If you
are shooting medium speed film or a digital SLR, then the converter is
more likely to catch detail that would not be captured without it, and
the larger the grain or pixel pitch, the more magnification you can use
with a TC.
--

John P Sheehy