Digital Billboard Brightness Measurement per OAAA Guidelines

Digital billboards have become a staple in modern advertising, lighting up highways, cityscapes, and public areas with eye-catching visuals. However, their high visibility also brings significant responsibilities, particularly regarding brightness levels. When not properly managed, excessive brightness can lead to driver distraction, light pollution, etc. As a result, organizations such as the Outdoor Advertising Association of America (OAAA) have established industry guidelines and measurement techniques to ensure that LED billboards are effective and non-distracting.

Key Metrics for Measuring Digital Billboard Brightness

Two key metrics are commonly used to measure the brightness of a digital billboard: nits and footcandles. While both are related to light, they measure different aspects and serve different purposes in the context of digital billboards.

Nits, also known as luminance, measure the brightness emitted from a display. Technically defined as one candela per square meter (cd/m²), this metric is key to understanding the brightness capabilities of the digital billboard, including how vivid or intense its output appears. However, nits alone don’t account for the surrounding environment. While a digital billboard may be inherently bright, its perceived brightness can vary significantly depending on ambient lighting conditions, such as those faced by viewers or drivers.

On the other hand, footcandles measure illuminance, or the amount of light falling onto a surface. This is the light that the human eye perceives, making it a more practical measurement for real-world conditions. Footcandles account for ambient light, weather, time of day, and nearby light sources, offering a more accurate representation of how bright a digital billboard appears to the viewers or drivers.

The OAAA advocates using footcandles as the standard for measuring digital billboard brightness. This preference stems from the desire to reflect how light is perceived in real-world settings. By accounting for ambient light, footcandle measurements ensure billboards maintain optimal brightness—neither too dim during the day nor excessively bright at night. Moreover, this method aligns with the actual viewing experience of drivers, capturing how billboards appear through windshields amidst surrounding light sources. Not only do footcandles provide a better characterization of billboard brightness, but they are also safer and easier to measure from a distance.

Digital Billboard Brightness Measurement as per OAAA Recommendation

To ensure a digital billboard is never overly bright for its surroundings, three key elements are essential:

(1) Maximum Brightness Limits (0.3 Footcandles)

The recommended maximum brightness level of 0.3 footcandles for digital billboards stems from guidelines by Dr. Ian Lewin, based on the Illuminating Engineering Society of North America (IESNA) standards to minimize light trespass. This limit is designed to reduce glare and prevent driver distraction, ensuring a much safer illumination.

(2) An Ambient Light Sensor

An ambient light sensor, also known as a photocell, is recommended to be installed on the billboard structure to monitor real-time lighting conditions. These sensors continuously measure environmental light levels, accounting for changes caused by weather, time of day, etc.

(3) A Dimming Software

Complementing the sensor is dimming software that dynamically adjusts the billboard’s brightness based on the sensor’s readings. This system creates smooth transitions as lighting conditions shift throughout the day, maintaining optimal visibility without overwhelming viewers or drivers.

For effective and consistent brightness evaluations, the OAAA specifies standard distances for footcandle readings based on billboard size:

Billboard Dimensions (ft.)	Distance to Measure from (ft.)
12 x 24	150
10.6 x 36	200
14 x 48	250
20 x 60	350

Measurements should be conducted at a distance corresponding to the billboard’s dimensions, with the light meter directly perpendicular to the billboard’s face. The typical measurement procedure begins by measuring the ambient light: use an opaque black sheet about 7 to 10 feet away from the light meter to block the light coming from the billboard and record a baseline reading. Then, add 0.3 footcandles to this baseline to calculate the maximum brightness limit. Remove the opaque black sheet and continuously monitor the billboard’s brightness for 3 to 5 minutes using the light meter to check if it stays within the established limit.

Interested to find out more about Konica Minolta Sensing light measurement solutions? Or perhaps require help finding the appropriate measurement solutions for your digital billboard or outdoor display application? Reach out to our team of experts now for a free consultation and get started with the right light measurement solution tailored to your needs.