Posted April 23, 2012
Cambrey: It seems to me that you are losing way too much light and sharpness, resulting in underexposed images with black too dark here and there. I keep my investigations going and hopefully I'll make up my mind within the next couple weeks.
The polarizer will sap light from entering the camera; however because that light is lost before it reaches the sensor and the exposure meters the cameras built in meter should already account for the light loss from the polarizer. So you shouldn't get underexposed photos from using it unless you start shooting in manual mode without the polarizer and then attach it and don't adjust your settings for the new light levels.