Originally Posted by
livedarklions
From the Epilepsy Society website:
https://www.epilepsysociety.org.uk/p...y#.XQ0i_YhKhph
"Between 3-30 hertz (flashes per second) are the common rates to trigger seizures but this varies from person to person. While some people are sensitive at frequencies up to 60 hertz, sensitivity under 3 hertz is not common."
Any more artificial goal post moving you want to do?
Also, I don't find a lot of really clear results when I google "hertz" and "bicycle light". The advertised specs tend to be lumens, not hertz, so I don't really know what the normal rate for these strobes are. I'm sure I'm seeing a lot faster than 3 hertz in the wild, but I really can't count much faster than that.
Wow, an Epilepsy thread. Awesome.
Canadian Epilepsy Alliance
Not all flashing lights or visual patterns will trigger a seizure, even in individuals who are photosensitive. The rate of the flashing light,the duration of the flashing, and the intensity of the light all play a part. A flash at a frequency of between 15 and 20 flashes per second is most likely to cause a seizure, whereas very few people are sensitive to a rate of 3 flashes per second.
So while I understand that some seizures have been reported as low as 3 hertz, as the extreme lower bound, and (possibly) some have been reported as high as 60 hertz as the extreme upper bound; The Epilepsy Alliance plainly states between 15-20 hertz is the most likely.
So following that: According to
NASA
Temporal Frequency. The rate of flashing has a powerful influence on the salience of flashing elements. The human eye is most sensitive to frequencies of 4-8 Hz (cycles/second). Very slow and very fast blinking are less attention-demanding than rates near that peak.
The stimulus graphed in b flashes faster (higher f) than the one in a. The stimulus in c has a lower depth of modulation (lower C) than the one in a.
Contrast, Depth-of-Modulation. The change in luminance between the peak and trough of the modulation also has a strong influence on the demand on the users' attention. The graphic element will have maximum salience if it goes from maximum luminance to minimum luminance in a cycle, at a frequency of 4-8 Hz. On the other hand, if the luminance contrast of the data element is low the blinking may be barely noticeable.
I will concede that there is
some overlap between the fraction of photosensetive Epileptics at least 2 standard deviations away from normal photosensetive Epileptics and the 4 to 8 hertz that bicycle lights are designed to for maximum attention grabbing ability.
You do realize that the fractions we are dealing with are getting into the 1 in 10's of thousands, right?
No moving goal posts here, just establishing the parameters of the equation for actual risk.
Stats were my favorite math class.
