Luminance Requirements for Signage Investigated by Researchers

Nov. 14, 2006
Signs that are too bright waste energy and cause light pollution

The Troy, NY-based Lighting Research Center (LRC) recently studied luminance requirements for backlighted, channel-letter signs. The organization’s research is significant because, to date, no signage-related luminance standards based on visibility exist in North America. In a recent LRC news release authored by Jennifer Taylor, signage is often brighter than necessary to try to compete with other nearby lighted signs. “This practice has drawbacks of higher energy use, light trespass, and light pollution,” explains Taylor.

LEDs were identified as a possible replacement for neon and fluorescent lamps in channel-letter signs, which, according to the LRC, consist of individual letters with a lighting system inside a metal case topped by a plastic diffuser. LRC Research Assistant Professor Jean Paul Freyssinier notes that LEDs - particularly red LEDs - can offer both energy and maintenance savings in these applications. Led by Freyssinier, a research team conducted a human-factors study aimed at determining a suitable range of luminances for red channel-letter signs. Findings revealed the impact of bright backgrounds on perceptions of sign brightness, with brighter backgrounds calling for brighter signs.

Standalone signs required a higher level of sign brightness than those with adjacent signage. “Most likely,” says Freyssinier, “adding the adjacent signs increased the overall luminance of the background, which led to a preference for a brighter sign.” Not surprisingly, a greater viewing distance also warranted brighter signage.

To read LRC’s reporting on this study, visit (

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