Ok here is a little about "Circular Polarizer" filters. Sample 1 Note the front windshield vs the side window Front has glare and not the side. Sample 2 Note the front windshield vs the side window Front now has not glare and side does. Sometimes I find the glare on windows to be over powering and will show you things in the reflection you don't want to see. Such as a building the rig is parked near. With the filter you can dial out some of these reflections by turning the filter. ---------------------------------- From "http://www.mat.uc.pt/~rps/photos/faq.polarizers.htm" Q: What can I use a polarizing filter for? A: The manufacturers will have us believe that you can block out any unwanted reflection in glass, water etc. You can *not* block out the reflections in metallic surfaces, since they do not polarize the light. But, although the manufacturers are right for the greater part, you will have to use the polarizer in the right way to get the above effect. This means, you will have to take your picture in a direction perpendicular to the sun (i.e. the line sun-reflecting surface has to be perpendicular to the line camera-surface), as is illustrated below: O sun o you / / / --------- reflecting surface You will be able to block out the unwanted reflections this way, dependent on the direction of the filter. When you're standing perpendicular to the sun, the effect will be maximum, slowly decreasing as you move in line with the reflecting surface and the sun. Then the effect will become zero. You can also use a polarizer to control the colour of the sky, ranging from light blue to dark blue/grey. Since the sky is scattered light and hence polarized, you can deepen the blue by removing light scattered by dust and molecules of, for example, water and hydrogen in the atmosphere(haze). In this way, you are able to let the clouds almost disappear or make them better visible. This also works best when you are standing on a line perpendicular to the line sun-earth. Also can be used for. As a 1- to 2-stop neutral density filter—e.g., to get a longer exposure speed in aperture-priority mode