Lighting / vision / Timing/strobe light effect

Sure is nice when you can swing the binocs and see which lights are DC-powered. At least you could back before high-frequency CFLs and LEDs.

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I have no own experience with this.

On largely lit ferries or cruise-ships, I could always detect the red/green lights with binoculars… before my central view was hit by macular degeneration.

They used binoculars; maybe the red light was registered as the entry to a dockside bordello and the green one to… I don’t know…

Lights (including incandescents) that are powered with 50/60 Hz AC vary in intensity and make a “string of beads” effect instead of a solid line when you waggle the glasses up and down. CFL lamps likewise I expect – but their frequency is around 40 kHz so phosphor persistence may prevent seeing it even if you swing the glasses fast enough. Most LED lights are also powered by pulse-width-modulated or variable frequency sources for efficiency. And even buoy lights may run on some form of AC these days.

I’m a bit red-blind which is certainly a nuisance on the water. This uncommon form of colorblindness (I’m a “protanomalous trichromat”) causes reduced intensity of all reds because some of the low-frequency detectors in the retina are lacking. It also leads to confusion between some shades of green and yellow.


That does not work for incandescent lights. The filaments don’t cool off that fast.
It also doesn’t work for ships that use AC powered anchor/deck lights, which I am guessing is a lot of them. It also doesn’t work for DC powered LED anchor lights depending on how often they are pulsed (PWM driver).

(there is a trick for calibrating an airplane tach by lining up with a streetlight at night and adjusting the RPMs to freeze the blades, I forget the formula)

That sucks with regard to reading instruments in red to maintain night vision. My wife drives a German car with red instrument lights. It’s a pleasure to drive at night. I drive a Chevy pickup truck and the instrument lights are BLUE! Why would GM do this? You’d think they’d know better.

Oh yes they do. Not to extinction of course, but enough to see a dimming effect. :slight_smile:

Fortunately night lighting isn’t an issue because all the gear is so over-bright to begin with that it still needs modification even after putting on a red filter. But I purely hate red LED displays in daylight, and I had to scrape the red paint off the warning icons in my '95 Subaru so I could see them in daylight.

Blue – yecchhh. It was suddenly fashionable because blue LEDs were developed long after the others (red was first, then orange, then yellow, then green – probably not a coincidence).

My BMW had great amber-red instrument lights, much easier on older eyes than the pure LED red that my next car had.

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Wife’s car is a 2009 Beemer X3 with all the bells and whistles. I hope we never have to replace it.
We’re straying way off topic but I think night lighting on bridges is as important as it is in aircraft cockpits. I wonder if the bridge lighting on the Helge Ingstad had an effect on the crew’s visual perception.

Doubt it, they did not use any monitors.


Some phonographs had, on the outside of the turntable, series of markers for 33, 45 and 78 rpm disks (the picture shows four series, I ignore what the fourth is for).

With only one incandescent bulb in an otherwise dark room, you could test and adjust the speed of the turntable, using the stroboscopic effect of the generally stable 50 or 60 Hertz of the power grid.

You start the turntable at a given RPM and then, the symbols of the corresponding series should come to a standstill.

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Fourth speed was probably 16 2/3, used for audiobooks for the blind.



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Looks like the one you show has a built-in neon lamp for the purpose, gives a sharper pattern.