What does a circular polarizer do?

If you've ever wondered what a circular polarizer does, and what it looks like before and after, then please read.

 

Combining Filters

1. No filter attached, no image editing.
2. After Circular Polarizer with Tiffen 812 Warming Filter on end of lens, no image edits.

 

Color Enhancement with Circular Polarizer

1. Circular Polarizer angle set incorrectly. Notice consistent blue sky and overcompensated "Character Sun."
2. Circular Polarizer angle set Correctly. Blue sky has gradient effect and "Character Sun" has vivid color as camera does not have to compensate for excessive light from real sun's location.

Head/Hair Halo Correction

Take notice that the overall shot feels like camera is under protected shade during 12pm sun. Circular Polarizer angle set correctly as glare is reduced and overall exposure is averaged better.
Also take note of center subject hair color. Normally subjects would have the top of the head show up as white/glare, but after the polarizer effect it reveals bright orange/red. If circular polarizer angle is set correctly, you see
the real color underneath the glare. BTW, subjects hair color was just dyed 1 week prior, so don't expect this hair color all the time. (shh...don't tell authors subject I told you so!)