In article ,
Davey writes:
On Sat, 19 Apr 2014 13:26:31 +0100
"Dave Plowman (News)" wrote:

In article ,
charles wrote:
So why don't they flicker when the studio is running at 625/50 -
since it's not locked to the mains frequency? The eye would see a
flicker at much lower speeds than 10 a second.

I'm not a physician. Could the brain sense flicker at less than
0.1Hz?

It's one of these things which seem to vary from person to person.
Many complain about flicker from some 50 Hz fluorescent lights saying
it gives them a headache. I can't say I've ever noticed it.


My wife complained about them even in the US, whereas they have never
bothered me anywhere. Except in China, where the hotel lights, all of
them, flickered at about 1.5 Hz.

No one can see 100Hz flicker - the limit is below 75Hz.
Animals with smaller brains can see higher frequencies,
and flies can see 1000Hz flicker.

With discharge tubes, a problem can be that they are partially
rectifying, resulting in 50Hz (or 60Hz) flicker, and most people
can see that. High intensity discharge lighting in shops was
often run on DC, to prevent this (prior to electronic ballasts).
There's a DC switching unit which alternates the DC flow every
switch-on, so you still get most of the expected lamp life.
This doesn't work with fluorescent tubes, because the mercury
tends to migrate to one end after some hours, leaving the other
end of the tube glowing only a very dim pink (argon gas).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]