[ale] OT: Light Management

[Michael H. Warfield]

On Sun, 2012-08-19 at 20:39 -0400, Michael Campbell wrote:
> On Fri, Aug 17, 2012 at 1:47 PM, Jeff Hubbs <jhubbslist at att.net> wrote:
> > On 8/17/12 12:28 PM, Jay Lozier wrote:
> >>
> >> Lighting affects people differently. Fluorescent lights can induce
> >> migraines in some, especially when the bulb is going bad. Also, the
> >> color temperature of fluorescents gives yellowish-green light that some
> >> find very irritating

> For me it's the damn flicker.  I can "see" 60hz, at least
> peripherally, and (to quote "Joe vs the Volcano"), they give me a
> brain-cloud.  I am lucky in that I have either worked from home where
> I can control it, or have been in an office friendly to me unscrewing
> the bulbs above me for the last few years, so I have incandescent
> where I am able.

One little point of order.  Bulbs that flicker that are operating at
"line frequency" (full size fluorescents, some LED's) flicker at 120Hz,
not 60Hz.  You have two zero crossings per cycle and two peak current
intervals (one in each direction) per cycle.  60Hz AC gives you 120
pulses of light per second.  This would be 50Hz AC and 100 pulses of
light per second in Europe.  In contrast, a classical "film" movie is
only 24 frames per second and NTSC Television (pre HD) is at 30 frames
per second (60 fields per second) but CRT's had a medium persistence
phosphor to reduce flicker.  You could STILL see the banding in CRT's
when a camera was shooting a screen.  That was basically 60Hz
stroboscopic effects.

Compact fluorescents operate had a much higher rate and are running off
switched supplies at much higher frequencies than that.  When
fluorescents start to give out, they tend to have plasma effects like
swirls and coils (especially in the monsterous 8' commercial ones) that
can have weird optical effects and give me a migraine.  Color balance
has a heavy effect on a lot of people though...

Regards,
Mike

> I use f.lux on my windows machines to gradually red-shift my monitor
> color at night which helps me a lot, too.  (And redshift on linux.)
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-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
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