In the context of images, a greyscale model represents a picture using only shades of grey, from pure black to pure white. There’s no colour information included. This is commonly used in black and white photography or to convert colour images into black and white.
- The greyscale colour model is used for:
- Converting colour images to black-and-white.
- Creating black-and-white images through cameras, scanners, and other input devices.
- Three algorithms are commonly used for greyscale conversion: the lightness method, the weighted average method, and the luminosity method.
- The greyscale colour model is not a simple linear scale from black to white but rather a method of converting colour brightness to reflect tonal relationships. When converting digital images to greyscale, each pixel is assigned a corresponding level of brightness based on its colour.
- When fully saturated spectral colours are converted to greyscale, their brightness typically ranges between 11% and 89%. For example:
- Red = 70%
- Orange = 40.38%
- Yellow = 11%
- Green = 41%
- Blue = 89%
- Violet = 74.06%
- Any RGB decimal colour value can be converted to greyscale. For instance, the RGB value for cyan converts to a greyscale value of 178, 178, 178. Similarly, HSB colour values can also be converted to greyscale, with the HSB value for pure yellow being Hue = 0, Saturation = 0, and Brightness = 11%.
Related diagrams
Each diagram below can be viewed on its own page with a full explanation.
