Why are older lightbulbs yellow/orange and newer ones white?



thought of this while night driving last night and seeing old cars with yellow lights and new cars with bright white lights.

In: Technology

Older light bulbs used incandescent technology. Basically they just heat up a wire until it glows. These were really inefficient and wasted most of their energy as heat. They also had a limitation that if you wanted to get pure white out of them you had to run them incredibly hot which shortens the lifespan.

Newer lighting technologies like HID and LEDs, in addition to being way more efficient, can put out a more pure white. This purer white gives more accurate color rendering of whatever it’s shining on.

It has to do with how controllable the light emitted is.

Old bulbs are very simple devices, they just run current through a wire that puts off light. The only way the old school bulbs have of controlling the color of the light is either a coating on the glass or by changing what material the wire is made from. These changes also change the properties of the bulbs so in the end the best option ended up being yellowish light.

Newer bulbs are much more advanced and more controllable so they can product a range of colors and even mimic natural sun light pretty well.

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.

Older lightbulbs are not yellow on purpose, it’s just the nature of the filament technology.

Newer LEDs can be made to be any color, so they choose to make them white. What you see as “white” is closer to the color of natural sunlight.

Color temperature is an option. You can walk into an auto part store and buy head lights that are either white or yellow.