Flicker factor guidance - Stadiums & Arenas

UEFA Stadium Lighting Guide 2023

Content Type
UEFA Guidelines
Stadium & Arena
Stadium Lighting
Enforcement Date

During broadcasts, we can often see that some illuminance systems cause the picture to flicker during slow-motion replays.

This is distracting and impairs the viewer’s experience, so it should be eliminated whenever possible. The circumstances that produce the flicker will vary depending on the modulation, the alternating voltage frequency and the camera frame rate.

The term ‘flicker factor’ refers to the amount of luminance modulation on a given plane during a complete cycle. It denotes the relationship between the maximum luminance value and the minimum luminance value over a full cycle and is expressed as a percentage.

Flicker: A rapid and repeated change in the brightness of light over time.

Modulation: A measure of light variation during periodic oscillations.

The flicker factor is calculated using the following formula:

Where E represents the illuminance level during a complete cycle.

In all but the most extreme circumstances, it is possible to eliminate the flicker seen during slow-motion replays. The table on the next page provides a general indication of the flicker factor values produced by various light sources.

A flicker factor of less than 3% will not generally cause problems for slow-motion replays of up to 300 frames per second. While the number of frames per second will vary depending on the technology used, a light source with a flicker factor of less than 3% will eliminate perceived flicker for most technology used within the sports television industry.

Illuminance flicker is commonly eliminated by installing electronic control ballasts or square-wave form ballasts in the illuminance system. This technology can generally be added to existing installations, as well as being available for new installations.

The flicker observed with very high numbers of frames per second can also be eliminated using computer processing. However, this method has other limitations.

The level of flicker considered acceptable is indicated in the tables in UEFA illuminance requirements.