[time-nuts] Hi Power LED Light power supply...
bownes
bownes at gmail.com
Tue Sep 18 18:11:12 UTC 2012
The local sandwich shop that I frequent recently switched to LED lighting. When I walk up to the counter I can see the flicker when people's hands are moving.
The same applies for LED taillights when a vehicle is moving as well as newer LED tower lighting.
Bob
On Sep 18, 2012, at 13:15, Hal Murray <hmurray at megapathdsl.net> wrote:
>
> lists at rtty.us said:
>> There are a *lot* of TV's out there that refresh at 60 Hz or less.
>
> Many years ago, we had a busted fluorescent light at work. I could see the
> flicker out of the corner of my eye. I found it annoying, so I'm a firm
> believer that some people can see flicker in some conditions. (Fortunately,
> it was in a location where I didn't spend much time.)
>
> Direct vision was not a problem. I assumed the lamp was running at 60 Hz
> rather than 120 and that peripheral vision was better at detecting
> flicker/motion.
>
>
> Wiki has an interesting page on this stuff:
> http://en.wikipedia.org/wiki/Flicker_fusion_threshold
>
> the rod cells of the human eye have a faster response time than the cone
> cells, so flicker can be sensed in peripheral vision at higher frequencies
> than in foveal vision
>
> But also:
> The maximum fusion frequency for rod-mediated vision reaches a plateau at
> about 15 Hz, whereas cones reach a plateau, observable only at very high
> illumination intensities, of about 60 Hz
> (I think that is backwards from the previous line. I'd guess somebody typoed
> rods-cones.)
>
> Note that LEDs without diffusion are high-illumination, so I'm not surprised
> if some people report flicker troubles. It would be interesting to
> investigate some examples. I wonder if they are 120 Hz or 60 Hz?
>
>
> More wiki:
>
> For the purposes of presenting moving images, the human flicker fusion
> threshold is usually taken as 16 hertz (Hz). In actual practice, movies are
> recorded at 24 frames per second, and TV cameras operate at 25 or 30 frames
> per second, depending on the TV system used.
>
> Even though motion may seem to be continuous at 25 or 30 frame/s, the
> brightness may still seem to flicker objectionably. By showing each frame
> twice in cinema projection (48 Hz), and using interlace in television (50 or
> 60 Hz), a reasonable margin of error for unusual viewing conditions is
> achieved in minimising subjective flicker effects.
>
>
>
>
> --
> These are my opinions. I hate spam.
>
>
>
>
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