In article
[long, interesting post deleted for space reasons - go back and read it]
I commented on the earlier posting about methodology, so will skip repeating
that, and just say that better wide-open performance (than stopped down)
with a converter-lens combination indicates low-speed problems with the
set-up, or seriously off-center optics (unlikely). I find the TC14C superior
to the TC14/14B for all combinations I have tried, except with the older
style 500mm f8 (the 14/14B is excellent, and better with this lens). It also
works VERY well with the 80-200mm f2.8 AF from one stop down. The TC300/301
is excellent with the MF (sliding shade) versions of the 300mm f2.8 and
400mm f3.5, and with one of the two 300mm f4 AF's I tried it with (with one
sample I got results similar to yours, with the other noticeably better results). The TC14A was good with the 180mm f2.8 AF, but why bother... (the resultant FL is not much longer or any faster than a 70-210 E zoom, and probably not any sharper [and that zoom is also pretty good on the 14A...]). The TC14A generally performs well on lenses it matches, as do the TC14/14B/14C. The TC300/301 generally performs well on the longer, faster EDIF teles. The
shorter teles are somewhat left out in the cold on 2X's, unless well stopped down (using the appropriate converter, the TC200/201 or TC300/301), alas
(the TC200/201 may be best used at smaller stops for gaining magnification
compactly in macro work...). Thanks for the post!
Hope This Helps