T3D Re: Why Cicrular Polarizers in some SLRs? (TECH-3D digest 389)

[bobh@xxxxxxxxxxxxxxxxxx]

RE: While Brian mentions 'OTF' off the film metering (used  by 
Olympus licensed from Minolta), it it not the prime reason. In the 
Leitz Leicaflex SL and Zeiss Contarex SLRs new positions for 
metering sensors at at bottom of the mirror box (film chamber?) 
were developed. This was done with a small half silvered 'hole' in 
main reflex mirror which has a small mirror behind it directing the 
beam down to the CdS sensors at the bottom. This extra mirror 
was the reason for needing a circular polarizing filter to avoid 
distortion of the reading. Most modern SLRs have adopted the 
same scheme for placing the sensors for both Auto focus and light 
measuring!
 BobH
Bob Howard (bobh@xxxxxxxxxxxxxxxxxx)
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