Warren Kato wrote:
>In a message dated 99-06-19 22:50:37 EDT, you, Jeffrey, write:
>> They [Cambridge]
>> list it as a Pentax to OIympus lens converter for $49.95. do these really
>> work? More importantly do they work well and if so it is something that
>> most camera stores sell.
>The problem with these conferters is that the distance from the lens mount to
>film plane is longer with Olympus than most other 35mm camera (called the
>register distance).
Correct. In the case of the OM, the register distance is 46mm.
>Therefore they have to add optical elements (negative
>diopters) to increase this distance optically.
On the other hand, the Pentax K mount lens should expect 45.46mm. I would
expect that in order to put Pentax K-mount lenses, you have to "decrease" the
distance by 0.54mm.
I don't know if there is any optical elements in the converter, but for $49.95,
one cannot expect too much from this converter.
For example, the Canon FD to EF mount (EOS) converter exists in two versions,
one without optical elements and the other with optical elements. The register
distance for the FD lens is 42mm while for the EF lens it is 44mm. In order to
put the older FD lenses on the EOS body, one needs to "decrease" the distance by
2mm. The FD-EF mount adapter without conversion lenses would not allow infinity
while the one with conversion lenses would become in effect a teleconverter for
the FD lenses. I understand the former adapter is much less expensive than the
latter. Canon itself does make such an adapter of the former kind.
In the case of the OM to EOS converter, the situation is more favorable. The OM
lens would expect a larger distance of 46 mm from the mount to the film plane,
so you just need to put a spacer between the EOS body and the lens. Basically
the OM to EOS adapter is just that. A precisely machined piece of a spacer
which has an OM body mount on one side and the EF lens mount on the other to fit
the EOS body. No optical elements whatsoever.
I might add that there is a Pentax 6x7 to Olympus body adapter. I don't know
that Cambridge sells the K-mount to OM or the Pentax 6x7 to the OM. If it were
the latter, the register distances are favorable. The flange to the film-plane
distances for the medium format cameras are larger than those for the 35mm SLR.
A relatively thicker spacer with the Pentax 6x7 body mount on one side and the
OM lens mount on the other side would do a trick and optical elements are not
needed.
In Japan, there are many potential buyers of these adapters thus either the
stores have them in stock or customers can order through the camera stores for
one. Again these adapters are for the most part made in Japan and we know who
make them. There are some adapter makers in Germany as well.
I think that there are many amateur photographers in Japan and in Germany who
want to try different lenses on the bodies they own. Particularly Leica lenses
on other 35mm SLR bodies.
We were impressed with Richard Schaetzl's experiments on the laser-pointer
attached OM bodies and lenses. The knowledge level of advanced amateur
photographers in Germany and in Japan seems to be pretty high. I think that in
the United States there are shortages of sophisticated amateur photographers
compared to these countries, which would make it inconceivable for the stores to
stock any mount adapters other than T-mount adapters.
Tomoko Yamamoto
mailto:tomokoy@xxxxxxxxx
http://www.charm.net/~tomokoy/
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