Does anyone know of a good reference explaining how
polarizing filters are used in photography? The main
use is supposedly to make the sky darker and more
color-saturated. What seems strange to me is that
they sell both linear and circularly polarizing
filters, and I haven't been able to find any information
about how photographers actually use one as opposed to the
other. It seems to me that a linear polarizer might
indeed have the effects claimed (if you aligned it
properly), but a circular polarizer
should do no more than throw away 50% of the light.
The guy at the camera shop says that the type of filter
you use just depends on the hardware you have on the
front of your lens, as though the two types were
optically equivalent. This seems like nonsense to me,
but maybe I'm missing something.