Nit Guns – The New Sheriff in Town for Brightness
One of the many changes involving LED technology and the sign industry is a new way to measure a sign’s brightness, specifically the unit of measure. The “candela” is being replaced by the “nit,” which equals one candela per square meter. Devices that measure nits have been around for a while, just under different names, according to lighting-industry consultant Terry McGowan, owner of Lighting Ideas Inc. (Cleveland). “No one knows why it’s called a nit gun,” McGowan said, adding that “the meter does look a little like a gun with a trigger and you do point it at something.”
Compared to earlier models of lumen meters, whose functionality depended greatly on the distance from the sign, interference from other light sources and the angle of measurement, the new nit guns are not affected as much by distance or by the angle of the gun and neighboring light interference. Simply pointing the nit gun at a sign set on white (the maximum lumination) registers a reasonably accurate measurement. Averaging six of the nit gun’s easier point-and-register measurements provides the industry-accepted, official reading.
Today’s more-affordable nit guns should enter widespread use in the electric sign industry as the new standard for brightness, the Illuminating Engineering Society’s (IES) RP 39-19 Recommended Practice: Off-Roadway Sign Illuminance, rolls out. The standard’s new brightness-level limit of 150 nits or 150 cd/m², represents the maximum luminance at night for legibility – not too bright and minimal glare.
McGowan, who also advises the IES, the American Lighting Association and the International Dark-Sky Association (IDS), feels the nit gun’s greater ease of use and accuracy will be vital as LED-lit signs – and particularly large EMC-display screens – proliferate. “The measurements will often have legal implications due to brightness ordinances,” he said. Sign companies will have to manage screens bright enough to see during the day (approximately 10,000 nits), but also dim enough (100-150 nits) to fall within nighttime maximums. Some localities have legislated even lower lighting maxes.
One last thing that McGowan finds interesting about nit guns and the role of measuring and maintaining brightness levels for signs is that organizations that used to be at odds with each other over sign brightness have now come together in agreement. The old adage, “the brighter, the better” no longer applies. “Too much brightness can adversely affect readability and create glare,” McGowan said. More recently, he added, the IES and federal highway regulations have concluded that brighter isn’t necessarily always better, moving so far as now to agree with even the IDS, whose purpose includes battling light pollution. The new nit gun should help to enforce that.