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Interesting article at Business Insider on why we don't like LED bulbs:
There's a handy trick for reading station signs that otherwise fly past in a blur as you travel in a high-speed train. Look at one side of the window and then immediately at the other side of the window. When you change your gaze, your eyes will automatically make a rapid jerking movement, known as a saccade. If the direction of the saccade is the same as that of the train, your eyes will freeze the image for a split second, long enough to read the station name if you time things right.
Saccades are very fast movements of the eyes. Their exact speed depends on the size of the movement, but large saccades can move the eyes at the same rate as a high-speed train. The image of the station name becomes visible because it is travelling at the same speed as the eye, and the images before and after the saccade are blurred and so don't interfere with the image of the sign. This shows us that our vision is still working when our eyes move rapidly during saccades.
Scientists used to think we could see no more than about 90 flashes of light a second but now we know it's more like 2,000 because the eyes move so rapidly when we change gaze from one point to another. During the eye movement, the flicker of light creates a pattern that we can see. And this has some surprising consequences for our health thanks to the way some types of lighting can affect us. In particular, it could discourage people from using more energy-saving LED lightbulbs.
Most lighting is electric and powered by an alternating current supply, which makes the bulbs continually dim and then brighten again at a very fast rate. Unlike filament lamps and to a lesser extent fluorescent lamps, LEDs don't just dim but effectively turn on and off completely (unless the current is maintained in some way).
The answer is not to make them less piercing?
(Score: 4, Insightful) by RedBear on Saturday July 29 2017, @10:15AM (3 children)
More important than the effect on human vision is the obnoxious effect of cheap LEDs on digital video sensors. It's my understanding that the latest professional LED "hot lights" for video work have frequencies around 20,000Hz so that no matter how high your filming shutter speed is the flicker won't show up visibly in the video. But with cheaper LEDs and even LED street lights and LED car headlights and tail lights a video often has to have an annotation saying "the flickering you see wasn't visible in person". It can be quite annoying.
And because LED devices can have various different flicker rates and digital cameras can use a very wide range of shutter speeds, the problem can be more difficult for modern filmmakers to deal with than in the old days when you might just sync to a 50Hz or 60Hz signal to deal with the flickering of a TV screen.
It's hard to fault LEDs for energy efficiency but they really are just barely becoming a usable replacement for traditional hot lights in terms of flicker frequencies and Color Rendering Index.
¯\_ʕ◔.◔ʔ_/¯ LOL. I dunno. I'm just a bear.
... Peace out. Got bear stuff to do. 彡ʕ⌐■.■ʔ
(Score: 2) by rigrig on Saturday July 29 2017, @01:09PM (2 children)
That is for fluorescent lights: they aren't suited to run on DC, and used to just run to the AC frequency, but with modern ballasts they can run at those frequencies.
If you want (professional) flicker-free LED lighting you can get it: LEDs run fine on DC, so any decent rectifier will do the trick.
The problem is when you get a bunch of cheapest-to-manufacture-as-possible LED bulbs: skimping on the built-in rectifier will leave huge ripples in the DC, causing the flicker.
No one remembers the singer.
(Score: 3, Interesting) by zocalo on Saturday July 29 2017, @02:58PM (1 child)
UNIX? They're not even circumcised! Savages!
(Score: 3, Interesting) by RedBear on Monday July 31 2017, @03:24AM
By a strange coincidence I just now clicked on a YouTube video of a TEDx talk showing a perfect example of that phenomenon. The giant screen behind the speaker is going nuts in the video. Cascading blank lines and other weirdness. Sharp lines between different sections of the LED array.
https://www.youtube.com/watch?v=6t6rn1a-t6E [youtube.com]
¯\_ʕ◔.◔ʔ_/¯ LOL. I dunno. I'm just a bear.
... Peace out. Got bear stuff to do. 彡ʕ⌐■.■ʔ