LRGB, short for Luminance, Red, Green and Blue, is a photographic technique used in amateur astronomy for producing good quality color photographs by combining a high-quality black-and-white image with a lower-quality color image.^[1]

In astrophotography, it is easier and cheaper to obtain good quality, high signal-to-noise ratio images in black and white. The LRGB method is used to work around this to get good color images. The color (chrominance) information from the color image is combined with the overall brightness from the black-and-white image.

The theory behind the effectiveness behind LRGB techniques has been related to the working of human color vision.^[3] The rod cells in human eyes are sensitive to luminance and spatial data, while the cone cells are sensitive to color. There are three types of cones: those sensitive to red, those sensitive to green, and those sensitive to blue. Thus, each element of LRGB targets one type of photoreceptor cell in the human eye.