| There are 2 kinds of sodium lamps. Low-pressure sodium lamps emit a single wavelength and they are the only kind of lamp that does not use LEDs, but which can match or exceed the energy efficiency of LED lamps. However, with low-pressure sodium lamps you cannot perceive any color. There are also high-pressure sodium lamps. They emit a broad-spectrum light, even if with an excess of orange-yellow light. You can perceive the colors of things with such lamps, even if not very well. However the high-pressure sodium lamps have a much lower energy efficiency than LED lamps. In Europe I have encountered mostly, or perhaps only, high-pressure LED lamps used for public lighting. I have used at home some low-pressure sodium lamps for certain purposes, but I am not sure if I have ever seen one like that used in a public space, here in Europe. Low-pressure sodium lamps typically use transparent glass bulbs, like incandescent lamps or any other kind of low-pressure gas-discharge lamps, e.g. neon lamps. High-pressure sodium lamps use special bulbs made of translucent alumina ceramic, because glass would not survive in those conditions. |