Some cities are taking another look at LED lighting after AMA warning

Re:Some cities are taking another look at LED lighting after... by scythe on Sunday September 25, 2016 @02:27PM (#12576596)

What matters isn't color temperature, but the presence or absence of light in the range 360-405 nanometers, which activates certain neurons in the retina that suppress melatonin secretion. This light can be "unseen" because visual receptors don't respond particularly strongly to it, so it can be masked by much stronger emissions of yellow light. However, it still has an effect. Color perception is irrelevant in this case.

http://press.endocrine.org/doi/abs/10.1210/endo-119-5-2201?j...

http://jap.physiology.org/content/110/3/619.short

Fires and the moon emit very little light at this frequency.

[ Parent | on HN ]

Re:Some cities are taking another look at LED lighting after... by keenerd on Sunday September 25, 2016 @02:59PM (#12576773)

405nm is violet. 360nm is UV. Yes, we are sensitive to it. But white LEDs emit none* of either.

*Future generation of LEDs might shift from indigo (445nm) to violet to improve color rendition, but cost will go way up and efficiency will go way down so I doubt it will be common. And some stores are already adding UV LEDs to their lighting in order to make florescents really pop.

Edit: and a reference, the datasheet for the latest and greatest XHP50 LED: http://www.cree.com/~/media/Files/Cree/LED-Components-and-Mo...

Spectral charts are on page 11. Peak emission is at 445nm. Beyond 415nm there is nothing.

Cheaper LEDs will use a longer wavelength of blue, typically around 475nm.

[ Parent | on HN ]