Newsgroups: sci.misc
From: hoey@zogwarg.etl.army.mil (Dan Hoey)
Date: 14 Jan 92 23:15:41 GMT
Subject: Re: red LED vision

lo...@APLPY.JHUAPL.EDU (Louis Vasquez) writes:

>If I take my red led digital clock in a dark room, and shake
>it.  It appears that the digits move out of phase with the clock.

I'm pretty sure this is an effect of the cones of your eye operating
faster than the rods, but the cones see only the digits (since they
need a lot of light).

ga...@hpldsla.sid.hp.com (Gary Koerzendorfer) and
orn...@kodak.kodak.com (Barry Ornitz) have both claimed this is a
stroboscopic effect due to the rapid pulsation in most LED displays.
I do not believe this can be true, because the same effect is visible
with a burning ember moved back and forth in the dark.

Dan Hoey
Hoey@AIC.NRL.Navy.Mil