thought of this while night driving last night and seeing old cars with yellow lights and new cars with bright white lights.
In: Technology
You have the answers here in more detail than I need repeat – old bulbs made a wire glow and new ones use blue LED’s through phospor gel to “correct” the blue to white. We refer to the colour of “white” light by the “Temperature” (in Kelvin, which is like Celcius/centigrade, but goes all the way down to “absolute zero”). It is the colour (simplifying) a wire glows at when it is a certain temperature. Yellowy whites are lower temperature (maybe 3200K) and bluer whites are higher, closer to 5200K.
There’s more to this though – different countries tend to prefer different colours of white. Colder countries like the yellowy whites more, hotter countries like the bluer whites more. This is ironic, as we think of the yellowy whites as “warmer” colours, but they represent a lower temperature!
And to go deeper down the rabbithole, we perceive “white” crudely. The old incandescent (hot wire) light sources had a higher “CRI” (colour rendering index) which refers to the “purity” of the white. You’ve seen colour changing lights which make “white” by mixing just red, green and blue. That’s a very low quality “white”. The sun, and incandescent sources have a lot more wavelengths in between. Our eyes are easily fooled, but cameras aren’t, and colours can look “flatter” than with high-CRI white lights.
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