The primary level of compatability is mechanical. The Oly 1.4xA actually
protrudes forward from the lens mount into the back of the lens mounted
to it. Other teleconverters allow fro some protrusion into them by the lens:
Oly 2xA 6 mm
Rokunar 2x 7 element 15 mm
Vivitar 2x-21 4 element 13 mm
Vivitar 2x Macro Focusing 11 mm
My guess is that it's easier to get good performance when one can put
the front of the converter close to the back of the lens. Oly was able
to go close by specifying which Zuikos would fit which teleconverters.
The 3rd part manufacturers didn't have that luxury. The 3rd party
converters come in a couple of generic flavors, cheap, short 4 element
designs and less cheap, longer 7 element designs. The 4 element ones are
pretty shakey. The 7 elements, particularly when the lens is stopped
down are actually useful. Most of the 7 element ones look like they came
off the same assembly line. The Tamron SP converters will only fit on
Tamron Adaptall lenses, which may have given them some advantage in
designing them, since they know what lenses they will be used on.
One generic answer is that pretty much any lens will fit on any 3rd
party converter except the Tamron SPs.
The second generic answer is that any lens with an Oly mount, Zuiko or
not, that projects less than 6 mm behind its mount will fit on the 2xA.
My 2xA is cosmetically close to mint, but does have some marks where
someone tried to mount a lens that was too deep for it and marked the
interior blacking paint. Fortunately, it didn't hit the front element.
The secondary level of compatability is optical. Any lens mounted on any
teleconverter will work, in the simple sense that the effective focal
length will be increased and the effective speed will be reduced by the
magnification factor. Since Oly knew than many shorter focal length
lenses would fit the 2xA mechanically, but did not list them, I think we
can conclude that it is optimized for and will give best results with,
lenses 100 mm or longer. It is certainly well known that it works well
with the 300/4.5. I suspect that Oly didn't recommend it for that and
longer lenses because the effective aperture makes them so dim as to be
difficult to focus.
The 2xA may be used successfully with 3rd party lenses that mechanically
fit it. All teleconverters degrade the performance of the lens. Check
out Gary's lens tests for several examples. Prudence would suggest
testing any lens you plan to use with any teleconverter with and without
it before doing an critical shooting with the combination.
Moose
Richard Hawkins wrote:
I know the 2X-A is only recommended for use with specific lenses ( 1)
50-250mm/F5 zoom 2) 100mm/F2.8 3) 135mm/F2.8 4) 135mm/F3.5 5) 200mm/F4
6) 200mm/F5 7) 100-200mm/F5 zoom). Is this because of clearance problems
with other lens rear elements or because of poor results optically with the
other lenses? Does anyone have sample shots on the web of pics taken with
the 2X-A and the recommended lenses? Has anyone attempted to use it with
other lenses than those that are recommended? How does it compare with other
2x teleconverters? Is there any known difficulties in using it with any
specific focusing screens? What should one expect to pay for one in
excellent condition?
Albert wrote:
Do the Tokina Teleconverters protrude, or no? Can I use my 50mm and
90mm with them?
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