Originally Posted by
Speedo
I have a feeling that the blinking light ==> inability to judge distance is old conventional wisdom. During the mid-70's there was a line of bike lights sold that had an incandescent bulb and a very low blink rate to conserve the battery. That was when I first heard the blinking rear light ==> difficulty judging distance. For that particular line of lights I can believe that it would be true. The blink rate was very low maybe 0.25-0.5 Hz. The cyclist could move a considerable distance in the off interval. If the rider was rocking the bike while he/she rode it could wreak havoc with some observer trying to connect the dots.
FWIW, many of today's flashing headlights really aren't any faster. You mention LEDs' low-power modes that are really superfast blinks, but that's a moot point since they appear steady anyway. There are also lights like Niterider's that go bam-bam-bam-bam-bam as fast as you can say it, which I'd never use because they're just too damned annoying (one of my friends has one and I can't stand being near it; I'd hate to be in whatever car that she parks behind at a stoplight).
But, like I said, many flash patterns just aren't crazy fast. As an example, Dinotte's slow on-off is the same frequency as the warning beacons you see in road construction zones. I have a couple Serfas lights that are the same way.