Originally Posted by hawk911

Notice the detail now present in the seats.

Originally Posted by Indycam

All pola filters rotate .
Non circular pola filters rotate .

A circular pola filter is a new type of pola filter that was made because some new cameras had sensors placed behind a mirror that had a pola affect on the light passing through the mirror . When the old linear pola filter was used on this type of camera the two crossed pole filters would become a N.D. (neutral density) filter . The light that would pass the first pola would only pass the 2nd pola if they were lined up . As soon as the 1st pola was rotated the polarized light would no longer pass the 2nd pola filter . So the sensor would be "in the dark" .

A circular polarizer is a old linear pola filter that has a "phase shift" filter behind it . The light passes through the pola filter , becomes "polarized" . And then the light goes through the phase shift filter , the phase shift filter takes the light that gets passed the pola and rotates the light rays so that the light coming out is no longer polarised .

http://www.nikonusa.com/Learn-And-Ex...age?appendix=C
"Circular Polarizing Filter
Converts linear polarized light waves to circular polarized light waves. Required whenever polarizing is desired using autofocus cameras and cameras that have semi-silvered reflex mirrors."

http://www.schneideroptics.com/info/...dbook12_15.pdf
"Highly efficient standard circular polarizing filter for all cameras with beam splitters in the light paths of their TTL exposure meter and with autofocus lenses. Circular polarization has the same pictorial effect as linear polarization, but allows for proper exposure metering and/or autofocus distance settings."