When to use a polarizer

Polarizer 101

A common question about using polarizing filters is, "Can you turn off polarization?" To better understand how a polarizing filter works, let’s take a quick look at its optical design. A circular polarizer (CP) has two pieces of polarized glass that are pressed together with the polarization film on each lens lying perpendicular to each other. Because of the way that CP filters are built,  you can adjust the level of polarization by simply rotating the filter in front of the camera lens one way or the other until you reach the desired polarization in your scene. 

Most polarizing filters feature an outer adjustment ring that you can move while the filter is attached to your lens.  So, now back to the original question, 'can I really “turn off” polarization on a polarization filter' and the answer would be "no" - a CP will always polarize some light when placed in front of a camera lens. The best you can do is change the strength of polarization in your image by rotating the filter counterclockwise (weaker polarizing effect) or clockwise (stronger polarizing effect) until you achieve the amount of polarization you want. But if you want to “turn off” polarization, just take the CP filter off of your camera lens, and try something like a