The dark autumn evenings reminded me of a particular street light in my neighborhood that’s an awful purple color. I finally dug into what causes that. The “white” LEDs are really blue LEDs with a phosphor-based coating on the lens. The coating is excited by the blue light and emits other wavelengths, approximating white light. If the phosphor coating degrades or delaminates then more blue light escapes, making the overall light look more blue-violet.
The post image is from an entry on the Dark Sky Consulting blog.
This recent research paper has some pictures of the actual failure on LEDs.
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Our city said they ordered the wrong lights. They knew it would look all fucked up but they said they were going to install them rather than purchase new or have no lights.
I used to install these for a living and let me tell ya: the failure rate of the first batch to bless the streets was staggering. I probably changed 1/3 of the first 1000 I installed because they turned GREEN. Understandably the public was in an uproar and demanded we switch back to high pressure sodium lights. We did not.
I actually love this color and it makes it easier for me to see at night compared to the washed out high pressure sodium lamps.
A ton of these are all around Phoenix, Arizona. Honestly it’s pretty cool, and looks much better than the boring old white lights.
