On 03/12/2016 11:10, Scott wrote:
As I mentioned elsewhere, I am experimenting with LED lighting.

I was having a curry with a former colleague last night, who mentioned
his father hates LED lighting for the following reasons:

1. The spectrum is too narrow thus depriving the body of the right
kind of light.

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

This isn't true of some brake lights on cars or pelican crossings which
give a really annoying brutal flashing effect in peripheral vision.

3. Because of the frequency (colour temperature?) the light does not
travel as far so streetlamps need to be placed closer together but.
Councils are not doing this for cost reasons, leaving blackspots in
illumination.

That is complete ********. The LED luminaires are more tightly
controlled than the old lamps which means if designed right there is a
lot less sideways glare and more light on the roadway. They do tend to
need to be closer together than some old types of street lamp.

The LEDs don't have to get much more efficient/cheaper before it becomes
possible to make them spaced the same as HPS/LPS fixtures.

The one criticism that you can make is that because of the very tight
control of sideways light spill it becomes more difficult to pick out
the future direction of a road lit by LED fixtures. You can really only
see them from a distance by the illumination of the supporting pole.

Is there any merit in these arguments?

Very little to none at all.

--
Regards,
Martin Brown