CPL filter for dummies

Okay, I got myself a nice cheap Massa 77mm circular polarizing filter and tried it out today.

Few facts that I discovered for myself about CPL filters:

• They remove some of light reflections
• They darken the image
• The image greatly depends on filter rotation on the lens

Here are two simple pictures that illustrate the principle behind the filter ( taken here ):

Now it must make sense that to achieve the desired "remove reflections" effect one must rotate the filter on the lens and asses the image in the viewfinder. Usually the filters are made that way so they can be rotated after being mounted on lens.

At last - couple of dummy images, one taken with and one taken without the CPL filter:

Note the sky reflections removed from windows of the building.