5 ms·

Tens of kHz is higher than our "normal" temporal resolution. I see crafted experiments push the critical flicker fusion rate up to almost 1KHz. You are still or

by avip 8y ago

Tens of kHz is higher than our "normal" temporal resolution. I see crafted experiments push the critical flicker fusion rate up to almost 1KHz. You are still order of magnitude off. You should blind test that number. That being said, obviously the fact we probably can't see 10KHz flicker, does not imply it has no effect on our well being.

mrob 8y ago
Flicker at high enough frequencies isn't visible directly, but only as phantom array effect with very fast eye movement and high-contrast light. Flicker fusion frequency isn't relevant. I couldn't see 10kHz flicker when I last tested it (with an LED and 555 timer), but I could see 5kHz flicker. The exact threshold will depend on the observer and the test conditions. I find high frequency flicker very annoying because the appearance and disappearance of the phantom array effect looks like unexpected motion to me, and if something is moving unexpectedly then it needs attention.
- rubatuga 8y ago
  Yep, and assuming we can sweep our eyes 150 degrees in 300 ms, we get a maximum angular speed. That means that the light source flickers on and off once in (150/0.3)/10000 = 0.05 degrees. The human eye can resolve at best 0.02 degrees. This confirms the proper order of magnitude. Edit: if you turn your head at the same time, my numbers above are too conservative.
londons_explore 8y ago
In the right conditions, very high flicker frequencies can detected by humans. It doesn't require any special abilities, just the right conditions. Consider a flickering streetlamp outside your house. Now imagine you have two sets of net curtains covering your window, 10cm apart. The net is very fine - say a 0.1mm mesh. If you sit next to the window working, and move your head back and forth, you will see a moire effect. If you sit 10cm from the curtains and move your head at 1 m/s, the 'flashing' you see is 50 Khz. If the light source behind the curtains is flickering at 49,995 Hz, you will see the resulting 5Hz flicker when the flicker from the moire effect and the streetlamp get multiplied. As a regular human, you have now made a 50kHz flicker detectable with no special equipment.
- jacobush 8y ago
  Wow! I must leave a useless thank you note. I would never have thought of that.
- deleted 8y ago
  [deleted]

by avip 8y ago

mrob 8y ago

Flicker at high enough frequencies isn't visible directly, but only as phantom array effect with very fast eye movement and high-contrast light. Flicker fusion frequency isn't relevant. I couldn't see 10kHz flicker when I last tested it (with an LED and 555 timer), but I could see 5kHz flicker. The exact threshold will depend on the observer and the test conditions. I find high frequency flicker very annoying because the appearance and disappearance of the phantom array effect looks like unexpected motion to me, and if something is moving unexpectedly then it needs attention.

rubatuga 8y ago
Yep, and assuming we can sweep our eyes 150 degrees in 300 ms, we get a maximum angular speed. That means that the light source flickers on and off once in (150/0.3)/10000 = 0.05 degrees. The human eye can resolve at best 0.02 degrees. This confirms the proper order of magnitude. Edit: if you turn your head at the same time, my numbers above are too conservative.

londons_explore 8y ago

In the right conditions, very high flicker frequencies can detected by humans. It doesn't require any special abilities, just the right conditions. Consider a flickering streetlamp outside your house. Now imagine you have two sets of net curtains covering your window, 10cm apart. The net is very fine - say a 0.1mm mesh. If you sit next to the window working, and move your head back and forth, you will see a moire effect. If you sit 10cm from the curtains and move your head at 1 m/s, the 'flashing' you see is 50 Khz. If the light source behind the curtains is flickering at 49,995 Hz, you will see the resulting 5Hz flicker when the flicker from the moire effect and the streetlamp get multiplied. As a regular human, you have now made a 50kHz flicker detectable with no special equipment.

jacobush 8y ago
Wow! I must leave a useless thank you note. I would never have thought of that.
deleted 8y ago
[deleted]