As a board member of the Fountain Hills Dark Sky Association, I am submitting this letter as Part 3 in the seven-part community education series, which is required by the International Dark Sky Association (IDA) for Fountain Hills to achieve the prestigious Dark Sky Community designation.

When buying new light bulbs, you might have noticed that lumens are being used more prominently to define brightness rather than watts. Why is that?

For decades, watts have been used to indicate the relative brightness of lights. This was a satisfactory approach during the time when incandescent lights (lights with a burning filament) represented the vast majority of light sources. However, watts are a measure of power used, not brightness; hence with the advent of new, more efficient lighting such as CFLs (Compact Florescent Lights) and LEDs, using watts to define brightness was no longer relevant.

On the other hand, lumens have always defined the intensity of light emitted regardless of the type of light source, whether it’s an incandescent lamp, LED, CFL or others. For reference purposes, a 100-watt incandescent bulb produces approximately 1,600 lumens of emitted light. The latest LEDs can produce the same level of light output using less than 20 watts.

One other technical term worth noting is nits. A nit is a measure of luminous intensity per unit area used to indicate the brightness of flat screen displays such as electronic message boards, computers, televisions, etc. Studies have shown that a brightness above 100 nits causes temporary blindness for drivers. For that reason, communities across the country, including Fountain Hills, have adopted the 100-nit maximum for electronic message boards.

More information is on our website at fhdarksky.com.