The Flicker Checker on Your Smartphone

a guest post by Lisa J. Reed, Lighting Designer

Graybar Lighting Audit image

When I was a young engineering student, I worked for the EADC – Energy Analysis and Diagnostic Center. This program employed college students to perform energy audits of manufacturing plants and commercial office spaces and then provide them a report full of Energy Conservation Opportunities (ECOs.)

One of our most common ECOs at that time was: replace existing T12 fluorescent lamps and magnetic ballasts with energy-saving T8 fluorescent lamps and new electronic ballasts. That was way back in the olden days. We no longer see T12 technology today… right? Unfortunately, way too many facilities still have those old lamps, but why?

In addition to the energy savings associated with doing this lamp/ballast upgrade, one added benefit is the elimination of "flicker." Often imperceptible to the naked eye, flicker can be quite problematic for sensitive individuals, causing headaches or even seizures. Flicker happens with the natural cycling of AC power, but with the higher frequency inherent in electronic ballasts, the fluorescent phosphors are not allowed time to dim and therefore flicker is eliminated.

Let’s assume you have already done the right thing and upgraded all of those old T12 fluorescent lamps and magnetic ballasts. Think you’re safe? Think again. Now there’s a new flicker source in town. Some (but not all) LED lamps can be downright obnoxious when it comes to flicker - especially dimmed LEDs.

But since flicker is more or less imperceptible to the naked eye, how do we check for it? Here are a couple of little secrets:

  • First, flicker is most noticeable in your peripheral vision, so wave your fingers back and forth at the sides of your head, and if they seem to strobe, you are dealing with a source of flicker.
  • If that test is inconclusive, try an electronic flicker checker. You probably have one in your pocket! Pull out the digital camera on your smartphone and point it at the nearest light source. If you see a series of bars or stripes on your display, that source is flickering. If not, you likely have a high quality LED with a compatible dimmer or at least an electronic fluorescent ballast, as shown in the photo on the far right, below.
2 Flicker Checker Smartphone LED Source flicker IMG 2 Flicker Checker on your Smartphone Magnetically T12 IMG Lighting Blog Electronically ballasted fluorescent image

LED source with flicker – note white vertical lines in photo

Magnetically ballasted  T12 fluorescent with flicker

Electronically ballasted fluorescent – no flicker

Try it right now on the light fixture above your head. Does it flicker or not? Let us know, and if it flickers call Graybar about replacement options!

Lisa J Reed photo - Lighting Blog

Lisa J. Reed has been attracted to lighting (like a moth to a flame) for 20+ years. She is the Founding Principal at Envision Lighting Design, LLC in St. Louis, where she designs, teaches, and writes about architectural lighting.


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