h a l f b a k e r y
Tip your server.
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
or get an account
Although incandescent light bulbs are inefficient, they
have the following wonderful property: As one slowly
decreases the power supply, the bulb's color temperature
naturally decreases, resulting in a lamp that smoothly
changes from whitish to yellow to red.
LEDs are efficient and long lasting,
and are *the* type of
new light for the foreseeable future. However, the give a
constant fixed color, even when dimmed.
This idea is to have several colors of LED inside of a single
enclosure, together with smart electronics which changes
how bright each LED as the power decreases. The
combination of these LEDs' lights would approximate the
color of an incandescent lamp at that brightness.
Although this might be accomplished using red, green and
blue LEDs, I expect it would be cheaper to use white,
yellow, and red LEDs.
Multi-coloured, remote controlled LED lights
Your idea is a subset of easily-available tech... [neutrinos_shadow, Jan 22 2017]
Light and Time: The Discovery of a New Photoreceptor System within the Eye
//we also have pRGC photoreceptors maximally sensitive in the blue part of the spectrum// [pocmloc, Jan 30 2017]
Page on blumens
Blue light sensitivity [notexactly, Feb 26 2017]
Mentions blumens. Also, don't search for blumens using Google without being prepared to see porn keyword spam pages. [notexactly, Feb 26 2017]
||You could probably get away with just two if both were dimmable: a white and a red. Just the white for daylight, combination for relaxation, and red for the middle of the night when you don't want to goose the pineal gland.
||^ And stick it on a timer so it dims on its own accord. Adjusting the dim would just advance or retard the timer.
||It's all an illusion, because even if the perceived colour is "safe" the spectrum is discrete not continuous. So basically LEDs are useless for human living illumination and always will be. Only black-body radiation can produce the spectral profile required.
||Why would you imagine that a continuous spectrum is necessary? It's interesting, though, to consider whether certain narrow wavebands are necessary for health. Obviously UV is relevant to vitamin D production, but it's generally assumed that the blueness/redness of light, if it has any effect, has it via the eyes - in which case any mix of wavelengths that gives the right perceived colour would do the job.
||Out if interest [Ian], does film behave differently to digital in that respect?
||It should be possible to construct an image sensor with the same spectral response as the eye (ie, three sub-pixels per pixel, with responses apprxoximating to the three cone types in the normal human eye).
||[mb] the eyes have separate blue-sensitive receptors for synchronising the circadian rythyms. This is why discontinuous spectra are a problem, because the percieved visual colour doesn't match the amount of blue receptor triggering.
||//the eyes have separate blue-sensitive receptors for synchronising the circadian rythyms.//
||Do you mean that they have blue-sensitive receptors other than the blue-sensitive cones used for vision? I.E. a set of non-visual blue receptors? Linky?
||How did I not discover those Phillips bulbs? *blushes*
||Having now read the page about those non-code non-rod
photoreceptors, I would definitely want my dimming LEDs to
have separate RGB phosphors, so that the blue could be
turned off first as the light dims (thus letting me sleep
better), then the green, then the red.