Polarizer, also called polarizing filter, or PL filter for short, is a color filter. The color removal function of polarizer is to selectively allow light vibrating in a certain direction to pass through. CPL Polarizer is often used to eliminate or reduce strong reflections on non-metallic surfaces in color and black and white photography, thereby eliminating or reducing light spots. CPL Filter is usually used on cameras to increase color saturation, making the colors of blue sky, green leaves, ridges and buildings more vivid.

According to the different mechanisms of filtering polarized light, polarizers can be divided into circular polarizers (Circular Polarizer, CPL Filter, CPL for short) and linear polarizers (Linear Polarizer, LPL for short).

Polarizers can eliminate harmful reflected light and improve the clarity and expression of images. Eliminate reflected light and eliminate light reflected from shiny surfaces such as water or glass. CPL Filter is specially used for AF focus cameras and digital cameras, and it is more convenient to rotate and adjust. In addition, it is also compatible with MF manual bodies.

Polarizer filter can control the polarization direction of a specific light beam. When natural light passes through the polarizer, the light whose vibration direction is perpendicular to the transmission axis of the polarizer will be absorbed, and only the polarized light whose vibration direction is parallel to the transmission axis of the polarizer will be left.

The reason why the polarizer is called a polarizer is that the polarizer facing the eyes of ordinary LCD monitors is frosted to dissipate surface reflections and scatter light to increase the viewing angle of the LCD monitor. For cameras, any scattering will cause light loss. The ideal state of the LCD used in projectors should be 0 degree viewing angle, that is, if you look at the LCD from a vertical direction, there will be no light. Of course, this is not achievable, but the closer to 0 degree viewing angle, the higher the utilization rate of light, so after replacing the frosted polarizer with a flat polarizer, the brightness of the projector to the wall will be greatly improved, about 50-80%, which is why we need to change the polarizer.