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posted by martyb on Saturday July 29 2017, @06:53AM   Printer-friendly
from the need-a-faster-flicker dept.

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?


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  • (Score: 2) by frojack on Saturday July 29 2017, @07:43PM (2 children)

    by frojack (1554) on Saturday July 29 2017, @07:43PM (#546392) Journal

    running at the typical 50Hz or 60Hz or AC mains

    Where would you see both?
    Entire continents are one or the other, not both.
    I'm guessing you only actually use 50HZ.

    I have nothing but LEDs in my home, (ok a couple seldom used CFLs left in odd places), and I never see any flicker.

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  • (Score: 2) by zocalo on Saturday July 29 2017, @08:38PM

    by zocalo (302) on Saturday July 29 2017, @08:38PM (#546415)
    I was being region agnostic, rather than implying you might see both in the same locale - I'm in the UK, so it's 50Hz all the way for me. The only individual countries I'm aware of with multiple AC formats are Japan (multiple frequencies) and Brazil (multiple voltages), although South America also has a fair bit of variation from country to country as well.
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  • (Score: 2) by moondrake on Saturday July 29 2017, @09:36PM

    by moondrake (2658) on Saturday July 29 2017, @09:36PM (#546433)

    Actually Japan uses both. 60 Hz in the south and 50 in the north IIRC. If you are close to the border between these areas, you might need both....