[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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