Re: Which Polarizer?

In article <1154365011.696392.242080@xxxxxxxxxxxxxxxxxxxxxxxxxxx>, AaronW <bj286@xxxxxxx> writes
David Littlewood wrote:
In article <1154309188.102766.249040@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
AaronW <bj286@xxxxxxx> writes
>The beam splitter is partially polarizing. That's why a linear
>polarizer might interfere. But the AE metering is affected at most
>about 1 stop. Since the meter is not perfect anyway, I might want that
>1 stop exposure bracketing. And under certain circumstances (color,
>angle, ...), circular polarizer will have exact the same AE problem as
>linear polarizer.
>
>For AF, the differences between circular and linear polarizer is very
>little.
>
>And because of the partially polarizing beam splitter, with a circular
>polarizer, sometimes the color effect I see in the viewfinder is
>different from that the sensor records when the mirror gets out of the
>way. I noticed this problem with circular polarizer and switched to
>linear polarizer.

First, a circular polariser can not have the same problems with a beam
splitter as a linear one; the polarisation direction is effectively
re-randomised

Not random, but the polarisation is rotated a certain angle. Each color
is rotated a different angle. But a certain color is rotated a certain
angle. If your scene is mostly a single pure color, e.g., green, the
green color is just rotated, the result is the same as a linear
polarizer, just a different angle. You can try this yourself by
stacking 2 polarizers together, and see this effect. Circular polarizer
works best on greyish scenes.

Not rotated, but rotating thus its angle is continuously changing; in other words "circularly polarized".

--
Ian G8ILZ
.

Relevant Pages

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