On Tue, 8 Dec 1998 12:51:16 -0800, "Charles Loeven" <cpl49@xxxxxxxxxxxxx>
jammed all night, and by sunrise was overheard remarking:
> <<it was that if you are going to use a spot meter, you better
> damn well have a circular polarizer>>
> Maybe I missed something. The circular polarizer is needed with a spot
> meter when a *semi silvered mirror is in the mix, No?
Yes and no. The circular polarizer is needed when a beamsplitter is
present in the mirror assembly of a camera, since this beamsplitter
itself is a kind of polarizer, so it won't properly see the light
output from a normal linear polarizer.
The reason for the beamsplitter is to use the same metering system for
prism and OTF (/off-the-focalplane) exposures. On cameras like the OM-4,
manual and spot meter readings are taken using the the "prism" metering,
while normal automatic shots are taken using OTF metering. This is an
improvement over the OM-2, which actually had two metering systems, a
photodiode system for OTF metering and a redundant CdS system in the
prism, like the OM-1, for manual readings.
Because the beamsplitter is not used during automatic OTF exposures, the
kind of polarizer isn't much of an issue on automatic, though the
exposure previewed could be much longer than the one actually set during
the exposure.
> The OM2000 has a spot meter. Does it have a *semi silvered mirror?
I don't know the OM-2000, but I would guess "probably not". While it has
a spot meter, it's a manual camera if I'm not mistaken. So no automatic
system, so no need for OTF metering. Of course, you could use the
beamsplitter technique anyway -- the old Canon F-1 used this, since it
allowed the manual metering to take place in the camera body, so you
didn't lose metering when you changes viewfinders (the rival Nikon F1 put
the meter in the prisim, so you lost metering if you changed to anything
other than the one or two prisms that had meters).
You need it for the OM-4, OM-PC/OM-40, and I believe the OM-77; you
don't need it for the OM-1, OM-2, OM-10, or OM-G/OM-20. Those are all
the bodies I've had direct experience with (waiting to get rich first
before I spring for that OM-3Ti).
--
Dave Haynie | V.P. Technology, Met@box Infonet, AG | http://www.metabox.de
Be Dev #2024 | NB851 Powered! | Amiga 2000, 3000, 4000, PIOS One
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|