Measurements & formulas

Luminance

A measure of the intensity of emitted light, which describes the amount of light passing through, emitting from, or reflecting off a surface. Luminance is not a perceptual measurement.

Luminance is distinctly different from color properties such as lightness, value or brightness.

How it affects UI design

Luminance relates to a device's unique screen brightness levels, as the amount of light emitted from the screen.

Highly luminous displays can cause adverse effects for users with light sensitivity (such as eye strain or migraines) when viewed in dark lighting conditions. It is recommended to support both light and dark mode as well as iOS increase contrast mode and Windows high contrast mode.

Sources:

  1. Luminance. ScienceDirect. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/luminance
  2. Alan L Gilchrist. Lightness and brightness. Current Biology (Cell Press Journal). https://www.cell.com/current-biology/pdf/S0960-9822(07)00878-0.pdf
  3. Luminance. Wikipedia. https://en.wikipedia.org/wiki/Luminance