Circular Polarizer Filter help

I recently purchased a Nikon D300 along with 18-200mm VR lens from nikon and a circular polarizer II also from Nikon. Upon taking pictures without the filter, the pictures turns out excellent. however, when using the filter, the pictures seems to be darken. more importantly, the skin looks very unhealthy pale and background color is not as vibrant as before. Please someone can let me know what I did wrong.

Did you spin the filter? If not that would explain your results, spin the filter until the color pops. Also those filters work best with the sun at a 90 degree angle relative to the lens.

Perhaps you are in manual mode, and haven't compensated for the loss of light - so the pictures will be under-exposed...? If you can, please post a sample image here, it sure would help in finding out what your problem is.

#1. Also, what kind of lighting were you photographing in? I have used a circular polarizer for indoor portraits, and the results weren't very pleasant.

#2. Check to see what the "White Balance" in your camera is set to. The wrong WB can produce photos with strange colors.

#3. Spinning the filter varies the intensity of its polarizing effect.