my camera from, linear polarizers don't work well with auto-focus type cameras because of the way the light hits the polarizer. The metering system of newer cameras work better with a circular polarizer.

(It was only $21!). No wonder I was having issues focusing.

Guess I'll price out a circular one now.

Camera shops are pretty good about that.

that sells used camera stuff and use the credit for a new circular polarizer.

My Sony F717 works fine with my linear polarizer.

Or "calculate exposure and focus".

From the <a href="http://www.luminous-landscape.com/tutorials/polarizers.shtml">Luminous Landscape</a>:

"There are two types of polarizing filters available • linear or circular. Linear polarizers are more effective and less expensive than circular ones. But circular polarizers are needed with just about any camera that has a through-the-lens metering system, or autofocus.

The reason for this is that both of these systems use semi-silvered mirrors to siphon off some of the light coming though the lens. If that light is linearly polarized it renders either the metering or the autofocus ineffective. This means that you're going to have to buy circular polarizers unless you're shooting with a pre-1970's camera, or a view camera."