User Guide > Rendering and Render Setup > Shading > Shading Nodes > Maya Render Nodes > Color Utilities >
Luminance
Converts color to grayscale. The luminance derives from a color value. Maya uses the following formula to calculate the luminance by adding the following amounts of red, green, and blue.
Luminance = 0.3 red + 0.59 green + 0.11 blue
Find this utility in the Create Bar (see Hide, resize or customize the Create bar).
To use this utility, see Use the Luminance utility.