Quote:
Originally Posted by ardecila
Isn't the color rendition of metal halide far superior to that of LED?[
I believe LED also needs a complex reflector to produce an even pattern of light instead of one that is marbled with the glow of each diode.
Personally, I have a strong nostalgia for the sodium-vapor orange glow, but I appreciate that the city is taking steps to be more environmentally-friendly.
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Not entirely sure of the color rendition. A quick check on the Wikipedia page pegs CMH at a CRI of 96 (100 is max, and is the rating of incandescent and sunlight) so its color rendition is indeed pretty awesome. LED is generally about 80, but qualitatively, since LEDs are frequently used for indoor lighting, I'm pretty sure that their color rendition must be more than sufficient. Fluorescent lights can range from a CRI of 51 to 89, for example.
You want to talk about terrible color rendition, low pressure sodium lights have a CRI of 5 and high pressure sodium are about 25.
Most LED streetlights that I have seen include no reflector or refractor whatsoever; the individual LEDs are usually fitted with lenses that refract their light and spread it out over a wide area.
The big win with LED is its durability and energy usage which drives down costs significantly, but that all goes out the window if CMH is a simple "screw-in" replacement, in contrast with the complete replacement of everything except the pole (and perhaps even the pole itself) that LED would require. LEDs probably only make sense as new installations, or where the entire fixture must be replaced, or where the poles are being taken down anyway on account of road work or streetscaping.