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

[Peter Homer <P.J.Homer@xxxxxxxxxxxxx>]

>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)

Usefull information but I dont think the silvering is the problem certainly
not full sivering which should have no effect on polarised light except to
reverse the rotation of circular polarised light. Rather it is the partial
reflection/transmission of the glass itself as I have already replied to
Elliots posting.      P.J.Homer




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