On Fri, 16 Oct 1998 02:28:39 EDT, PCACala@xxxxxxx wrote:
snip...snip...
>One should take that S stuff with a grain of salt. For example, the 35-70mm
>f/4.0 Zuiko Auto Focus Zoom (a fine example of which I'm putting up for sale
>within the next two days) is the same optical construction* (plus a prism or
>pellicle) as the 35-70mm f/4 S Zuiko Zoom. And the 100-200mm f/5.0 S Zuiko
>Zoom is a fine performer, indeed. In retrospect, the very first OM System
>Zuiko Zoom, the 75-150mm f/4.0, probably deserved an "S" moniker.
>
>Gary Reese
>Las Vegas, NV
>
>* OK, If you read this far, I'll accept the fact that a single element in the
>formula is a bit thicker in the AF version, perhaps to compensate for the
>prism or give increased back focus to allow for a prism in the light path.
AFAIK two prisms kitted together are in the light path to the film,
the kitting plane mirroring part of the light rays downward to the AF
sensor.
The two prisms together result in a planparallel glass plate between
the original rear element of the lens and the film plane. I would have
expected one of the positive (convex) elements in the lens to be
_thinner_ to correct for the longer lightpath to the film.... or is it
a concave one being thicker?
Frank van Lindert
Utrecht NL.
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