The city of Seoul has introduced South Korea’s first recommended standards for LED display brightness, its municipality has said.
The South Korean capital’s metropolitan government said the move had been taken to “alleviate fatigue among pedestrians and drivers, address brightness disparities between areas, and mitigate public inconvenience”.
It added: “The new guidelines come in response to a rise in complaints about eye strain and excessive brightness following the designation of areas such as COEX, Gwanghwamun Square, and Myeong-dong as free display areas for outdoor advertising.”
The move was announced at the end of March and set a 7,000 cd/m2 cap as the recommended standard for outdoor LED displays. It also establish detailed, time-based night-time limits, making Seoul the first city in Korea to implement such specific luminance guidelines for outdoor LED displays.
The city stated that the measure is intended to supplement existing regulations – which allow relatively broad brightness ranges – by introducing clearer, more practical criteria to reduce visual fatigue caused by overly bright screens while maintaining advertising effectiveness.
To ensure objectivity and practical applicability, the city conducted on-site measurements of brightness levels at 52 major LED billboards across Seoul between January and March.
Based on these findings, standards were set depending on the display area, which is categorised as medium (between 30-225m2) or large (more than 225m2).
In addition, the guidelines introduce content design recommendations aimed at reducing glare.
For static advertisements, large areas of high-brightness white should be minimised, the city has recommended, and overall brightness levels should be reduced.
For advertisements with transitions, abrupt contrast changes should be avoided in favour of smooth, gradual transitions, it added.
The standards took effect from 1 April, and are expected to lead to a 15% saving in energy as well as an improved environment for citizens.
To support implementation and compliance, Seoul has also adopted automatic brightness control systems, which adjust screen luminance in real time based on ambient light conditions.
The guidelines also took effect on 1 April and apply to all outdoor LED displays with a surface area of 30m2 or larger.
These require that automatic brightness control systems be installed as a standard requirement. Systems should include a fail-safe function that automatically switches to low brightness or turns off in case of sensor or control system failure. All existing displays are recommended to install these systems.
The control system should reduce brightness in stages (typically 1-16 levels). Based on surrounding light conditions, the automatic brightness control system is also required to use an ambient light sensor to help reduce light pollution while improving visual comfort and energy efficiency, the city said.
The ILP’s 2023 guidance on this issue, ‘PLG05 The Brightness of Illuminated Advertisements’ can be downloaded from the ILP website.
Image shows night-time measurements being taken at Seoul’s Kyowon Naewei Building, courtesy of Seoul Metropolitan Government
