In article ,
Steve writes:
Andrew Gabriel wrote:

The mean brightness is still the same, since the mean current must be
the same,


Actually LEDs get slightly more efficient at higher current, so
the mean brightness is higher.

That certainly used to be true, but again for the Luxeon jobbies we use,
it ain't anymore.

Furthermore, it appears that eyes don't perceive mean brightness,
but perceive something which is between the mean and peak brightness,
so a flashing light will appear brighter than a steady light of the
same mean brightness (over some frequency range).

Neither of these effects is very large though.

Is this a medical fact ? In recent discussion on sci.elect.design, this
effect was poo-poohed by several of the engineers in there whose
opinions I would trust.

I've seen it stated on a number of occasions. I have not personally
tested it but it sounded plausable. BTW, the frequency range over
which it works is not wide. It needs to be above the optical fusion
frequency (varies from one person to another, but never higher than
70Hz), and below the frequency response of the receptors and optic
nerve (which I believe is always over 100Hz, well over in some people).
One person I spoke to about it a while back didn't think the frequency
response of the optic nerve was the upper limit for the effect to work
(thought it was higher). These frequences vary a little across the
field of vision too, and with other factors.

--
Andrew Gabriel