Lars, you have a real gift for explaining thing succintly and with
clarity. You must be formidable in your native tongue. Thanks.
Giles
> Don't feel dumb--this is a bit complicated. When light has passed
>
> trough a linear polarizer, it is (you guessed it) linearly polarized,
>
> i.e. all the waves wave in the same direction. (Light waves are
>
> transversal, at 90 degrees to the direction of propagation, not longi-
>
> tudinal like sound waves.) Now, light is also partly polarized when
>
> it passes through a semi-silvered mirror. Many TTL metering
>
> cameras meter light which has gone through a semi-silvered spot
>
> on the main mirror. If by chance the two directions of polarization
>
> are close to 90 degrees from each other, the light will be partially
>
> extinguished and the meter will give an incorrect value.
>
>
> A circular filter polarizes light in two directions at a right angle
>
> to each other, so that this effect disappears. But in order to get
>
> a pola effect on the <italic>subject,</italic> you must rotate the
> filter just as with
>
> a linear polarizer!
>
>
>
> Vänliga hälsningar/Best regards
>
> Lars Bergquist
>
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