When I refer to % flicker, I am talking about the modulation % as defined by IEEE 1789-2015 and some documentation from the Illuminating Engineering Society [0][1]. More correctly, invisible flashing is known as the stroboscopic effect or phantom array effect.
Two factors are often used to describe flicker for lighting:
- Modulation %, a.k.a. % Flicker [The height or modulation of the waveform, formula is 100% * (A - B) / (A + B)]
- Frequency [self-explanatory]
Flicker Index is also used (refer to [1] page 7 for more info) but rarely.
Duty cycle is not considered relevant, as you mentioned.
Some tools designed to measure lighting, such as my UPRtek CV600 [2], spit out % flicker, frequency, and flicker index, in addition to a bunch of spectrophotometry metrics. It's also pretty easy to calculate the modulation % with an oscilloscope and photodiode, it's just Vp-p / Vmax.
IEEE 1789 [0][1] roughly says that the higher the flicker frequency, the more acceptable it is to have a high modulation %. If you look at the graphic on [1] page 18, you can see this relationship. The white area is considered unsafe, the yellow area is "low-risk", and the green area is "safe." I don't 100% agree with this personally, as most incandescent lighting, with around 6-11% flicker at 100-120 Hz, would fall into the unsafe or low-risk category. But the Soraa product is definitely in the unsafe category.
For reference, I plotted my product (Bedtime Bulb) against an incandescent A19, Lighting Science's Goodnight A19, and Soraa's Healthy A19 on an IEEE 1789 graphic [3] with a Python tool I'm developing, Beautiful Flicker [4]. You can see that this incandescent, measured around 10%, is on the border between unsafe and low-risk by this standard.
I don't think I could have wished for a better answer, thank you. Love it when a new area opens up to me like that! While I'm not active within lighting per se, some of our customers are, and this will help me understand the complexities of their products better. So, thank you, it does help!
Two factors are often used to describe flicker for lighting:
- Modulation %, a.k.a. % Flicker [The height or modulation of the waveform, formula is 100% * (A - B) / (A + B)]
- Frequency [self-explanatory]
Flicker Index is also used (refer to [1] page 7 for more info) but rarely.
Duty cycle is not considered relevant, as you mentioned.
Some tools designed to measure lighting, such as my UPRtek CV600 [2], spit out % flicker, frequency, and flicker index, in addition to a bunch of spectrophotometry metrics. It's also pretty easy to calculate the modulation % with an oscilloscope and photodiode, it's just Vp-p / Vmax.
IEEE 1789 [0][1] roughly says that the higher the flicker frequency, the more acceptable it is to have a high modulation %. If you look at the graphic on [1] page 18, you can see this relationship. The white area is considered unsafe, the yellow area is "low-risk", and the green area is "safe." I don't 100% agree with this personally, as most incandescent lighting, with around 6-11% flicker at 100-120 Hz, would fall into the unsafe or low-risk category. But the Soraa product is definitely in the unsafe category.
For reference, I plotted my product (Bedtime Bulb) against an incandescent A19, Lighting Science's Goodnight A19, and Soraa's Healthy A19 on an IEEE 1789 graphic [3] with a Python tool I'm developing, Beautiful Flicker [4]. You can see that this incandescent, measured around 10%, is on the border between unsafe and low-risk by this standard.
Hope this helps!
[0] IEEE 1789: A new standard for evaluating flickering LEDs?: https://www.dial.de/en/blog/article/ieee-1789-a-new-standard...
[1] Flicker: Understanding the New Recommended Practice (PDF) https://www.energy.gov/sites/prod/files/2015/05/f22/miller%2...
[2] UPRtek CV600 https://www.uprtek.com/en/product/SPECTRAL-COLOR-METER/CV600...
[3] IEEE 1789 Graphic Comparing 4 Light Sources https://github.com/yeutterg/beautiful-flicker/blob/master/ou...
[4] Beautiful Flicker https://github.com/yeutterg/beautiful-flicker