On 03/12/2016 17:16, Dave Plowman (News) wrote:
In article ,
Martin Brown wrote:

The LED colour rendering isn't quite right but 2700K tungsten lighting
is nothing like the natural light from the sun at 5000K.

Care to say just how you're measuring that sun? The colour temperature of
daylight varies by the time of day and time of year. Even before clouds,
etc.

That is roughly speaking the characteristic temperature of the suns
surface. Although very near sunset things get a lot different with
stronger red direct components and paradoxically a higher proportion of
scattered UV relative to the falling light levels immediately after
sunset so that some things appear to fluoresce as it gets darker.

Colour film
sees the difference but the human eyes white balance auto adjusts.

Basically the body might need some UV exposure per day for vitamin D
synthesis but neither LED *nor* conventional incandescents provide it.

2. HIgh frequency flicker, higher than fluorescents possibly
triggering migraine.

Persistence of vision and long phosphor glow time means that what little
flicker there is in LED lamps is negligible. They stay lit a
suprisingly long time after switching off. Incandescents also flicker
slightly at 100Hz.

I'd say an LED 'stays lit' because of its power supply. Not intrinsically.

Well yes, but since all LED domestic lighting is a PSU driving the LEDs
the result is that they do not flicker. OK some really dire cheap crude
Chinese ones might but nothing properly designed will.

--
Regards,
Martin Brown