What Is a Color Filter Array?

A color filter array is a group of miniscule color filters installed on the pixel sensors of digital cameras. These sensors are incapable of detecting low-intensity light, or light with no color wavelength specificity, so they are unable to separate light into different colors. A sensor with a color filter array is used by the camera to detect the light's wavelength and create a color photograph.

Digital cameras utilize rectangular-shaped arrays of light sensors known as pixel sensors. Pixel sensors contain what is known as a photosite cavity, or photodiode. When a camera's shutter button is pressed, light particles called photons enter the photosite.

Photosites are monochromatic, meaning they can only detect black and white. By itself, a photosite array cannot determine the amount of color that each photosite cavity picked up during exposure. To make a color photograph, a green, red or blue color filter is placed over a photosite. These colored filters only allow light of the same color into the photosite cavity.

One common type of color filter array used in digital cameras is the Bayer color filter array. The Bayer color filter array is a grid or mosaic pattern that consists of rows of alternating red, blue and green filters that are installed over each photosite on a camera. The mosaic pattern has twice as many green filters as red or blue filters. This is because the human eye readily picks up green, or is more sensitive to it than to red or blue light.

The mosaic pattern is converted by a program stored in the digital camera and called a demosaicing algorithm. Demosaicing algorithms take the data obtained by each color filter on the photosite and combine the neighboring pixel colors to create a color picture. This process creates a higher-resolution picture, or makes a clear, crisp image without a lot of distortion or “noise".

Other types of color filter array configurations include the red, green, blue, white (RGBW) sensor matrix and the cyan, yellow, green, magenta (CYGM) sensor matrix. RGBW sensors have a white or transparent light filter that allows photosites to respond to every color of light. A CYGM sensor uses secondary colors that are made when two primary colors are mixed together, such as mixing red and green to get yellow. This type of color filter array allows more colors of light or incidental light to be detected by the camera, often with vivid photography results.