ISA worked with noted lighting expert Dr. Ian Lewin of Lighting Sciences to help the industry develop scientifically-researched, understandable recommendations for EMC brightness.
ISA published this research in Night-time Brightness Level Recommendations for On-Premise Electronic Message Centers, which details what this means and how to measure it.
An executive summary is also available of the full report from the Sign Research Foundation.
The report recommends that EMCs not exceed 0.3 footcandles over ambient lighting conditions when measured at the recommended distance, based on the EMC size.
The report also highlights EMC case studies of how communities throughout the U.S. have used these recommendations to develop sign codes that meet community concerns while allowing businesses to use these tools.