[LRFlex] Re: Polarizer
- From: Kent Christensen <lkchris@xxxxxxxxxxxxx>
- To: leica_reflex_forum <LeicaReflex@xxxxxxxxxxxxx>
- Date: Mon, 17 Jan 2005 10:48:52 -0700
re: If I am not mistaken circular polarizers are required only in the case of
autofocus systems, manual focus lenses can be used with the original style
polarizers which you may own already. (Steven)
No, I think you're off one technology generation.
Circular polarizers are generally required with through-the-lens metering.
Linear can be used with other metering.
It's not focussing type, it's metering.
For this forum, then, it's circular from SL on.
Here's the word from Leica in the 1983 "Leica R-lenses" booklet:
"The previous exclusively used linearly polarising filters have been replaced
by Leitz circularly polarising filters to simplify operation of the LEICAFLEX SL and
LEICA R models (cameras with light metering through the lens), because the use of
circularly polarising filters saves the cumbersome corrections necessary with
linearly polarising filters. This is due to the type of light metering through the
lens used in the Leica s.l.r. cameras. With the selective exposure measurement of
the LEICAFLEX SL/SL2 and the LEICA R3 the light necessary for the measurement is
branched off by means of a physical beam splitter (the semi-silvered hinged mirrors
of these cameras). This also applies to the two exposure measuring methods
(integrating and selective) of the LEICA R4. Because these beam splitters
themselves act as polarizers, the measuring result when normal linearly polarizing
filters are used is falsified: unless corrections are introduced, exposures will be
wrong.
The situation is similar with the two measuring methods of the LEICA R3/R3-MOT
(also integrating and selective). In these camera models, however, the
proportion of the total light necessary for the exposure meter that reaches the
measuring cells in the bottom of the camera through the semi-silvered hinged
mirror (pyhsical beam splitter) depends on the measuring method. But the two
measuring cells above the focusing screen are unaffected.
With the circularly polarizing filter, on the other hand, the measured exposure
value can always be directly accepted. Only circularly polarising filters are
therefore recommended for use on the LEICA R models."
Kent Christensen
Albuquerque
SL, R3, R8
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