ELECTRONIC MESSAGE CENTERS (EMCs)
Electronic Message Center (EMC)/on-premise sign advertising a bank that is
located on the same premises as the sign
Digital billboard/off-premise sign advertising an automobile business in another
© International Sign Association 3
The International Sign Association (ISA) retained noted lighting expert Dr. Ian Lewin of Lighting Sciences to help the industry develop scientifically researched, understandable recommendations for EMC brightness. Dr. Lewin was a past chair of the Illuminating Engineering Society of North
America (IES), and was greatly respected within the lighting field. His work for ISA was conducted with the input of experts within the sign industry.
As a result of his research, Dr. Lewin recommended two different brightness settings based on whether the EMC was located in an area of
high or low ambient light. After field testing and utilizing Dr. Lewin’s recommendations, it was determined that using the more conservative
recommendation is appropriate in areas of both low and high ambient light. In order to simplify Dr. Lewin’s recommendations, and to take
a more reasonable approach to ensure that EMCs are sufficiently visible but not overly bright, it is recommended that EMCs not exceed
0.3 footcandles over ambient lighting conditions when measured at the recommended distance, based on the EMC size.
The research and the recommendations contained in this report pertain only to EMCs, not traditionally internally illuminated signs, such
as these channel letter and neon signs below. EMCs use a different lighting technology than most of these types of signs, and as such the
scientific approach differs.
Community leaders should understand that, while it is recommended that brightness measurements be taken perpendicular to the sign,
sign viewers rarely see the sign at that same perpendicular approach. At any viewing point away from or off the forward angle, the apparent
brightness will be reduced. In other words, the measurements will capture the recommended brightness levels, but, unless viewers are
looking at the sign directly perpendicular, they will not perceive the brightness at the full level.
We have provided recommended statutory language and tips to measure brightness with and without control of the EMC. If you need further
assistance, feel free to contact ISA, email@example.com or at (703) 836-4012 to answer any of your EMC questions.
FOOTCANDLES VS. NITS: WHICH MEASUREMENT IS BETTER?
This document recommends communities adopt illumination measurements in footcandles as compared to nits. Here are a few reasons
why more than 200 localities and many state departments of transportation have adopted the footcandle measurement for EMCs:
Measures illuminance Measures luminance
Accounts for ambient light conditions Measures only the amount of brightness emitted
Luxmeter measuring device $100 Luminance spectrometer (nit gun) – $1,000
“Twilight” measurement possible Does not allow adjustment based on ambient light
Measures light impact and appearance Does not measure appearance
Works with roadway lighting standards Difficult to measure accurately
Easier to check and enforce Difficult to enforce
* While the main advantage of using nits as compared to footcandles is that daytime measurement is possible,
EMC brightness is typically more of an issue at night.
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