Cokin P171 VariColor Red/Blue is a colored light filter. It is used together with a polarizing filter to change the color in the toning range from red to blue. Reflected light rays become polarized.

Polarizing filters are used to filter the light rays that enter your camera lens. They can remove unwanted reflections from non-metallic surfaces, such as water or glass, and saturate colors to provide the best contrast.

If you combine the P171 VarioColor with the neutral polarizer P164 (or P160), you can change the color by rotating the neutral polarizer. For example, depending on the relative rotation of the red-blue filter P171 VarioColor and the neutral polarizer P164, the reflection acquires either a red shade or a blue shade. The effect can be seen in the viewfinder and depends on how the filter is rotated and its orientation in relation to the sun.

These Cokin color filters can be used in conjunction with other Cokin P-series filters.