The light on left costs under $20 (battery included) and includes USB-C charging… Handy for brief uses.
The light on right costs about double (battery not included), no USB-C, but it has regulated output, very low Flicker Index, and custom LED options.
They both fall into the “no risk” category. What does this tell me? Other than knowing a lower score is “better,” what does it mean in practice?
Do you see a difference with your eyes? It’s often said different people have varying degrees of sensitivity to this sort of thing.
(One of your images is flipped upside down)
oops, now fixed, thank you 
Flicker Index goes beyond basic PWM, it is a calculation that considers both the Frequency and the Modulation Depth.
not an expert, but this is not about being able to see the Flicker… its more about the biological effects of long term exposure to Flicker.
For example, Office Workers who sit under lights with High Flicker Index tend to suffer from more episodes of Migraines and Eye Strain.
there is more deail about Flicker Index on google… I dont have a specific authoritative link to point you to… but the one metric Ive come across, to use as a reference, is that Flicker Index below 0.0500 is considered not to have negative biological effects.
I wonder if using a flashlight with a high index for, say, an average of 20 minutes per day could cause any “negative biological effects” ??
if you are not experiencing symptoms:
eye strain, headaches, fatigue, seizures
then I dont think you need to worry with such a low exposure duration
If Im going to use a light as an ambient light source for long duration, I would choose the one with a low flicker rate, such as my D3AA,
instead of my TS10, which has a high flicker rate
but I dont worry about using my TS10 for EDC where the light is on for brief periods. Such as looking for stuff in a box or a dark closet… or other short tasks of just a few minutes at a time.
I do consider Flicker Index as one of my flashlight selection criteria. It is gratifying that my Skilhunt H150, Emisar D2, and Emisar D3AA have very low Flicker Index.
My TS10 has high Flicker Index, but I still like to use it. Its my favorite form factor.
