2014/07/19

Turning the bathroom into an operating theatre.

My family have accused me of turning the bathroom into an operating theatre, because I changed a light bulb. The light in the bathroom contains two bulbs, and for years they have been normal incandescent light bulbs (the type with the coil which glows).

One of the pair burned out and I thought I'd so some energy saving so I put in one of those replacement neon lamps, coiled around itself to make it fit in the same space as a normal incandescent lamp. I noticed it had a bluish tinge, but thought nothing of it.

There was a small revolution, it was decided by the rest of the family that the neon light made the bathroom look like an operating theatre or mortuary. Every single time that light was switched on I got a "this is a horrible terrible light" comment. Every single time!

Eventually I gave in and bought a warm white LED lamp.

But why was the neon bulb so badly recieved? I have a spectrometer I use for work, so I decided to look at the spectrums. Hells bells if evolution doesn't come into it!

A spectrum just shows the combination of all the colours in a light source. There are an infinity of them, even in the visible part. From deep violet to deep red, passing through various blues, greens, yellows and oranges in the middle. So you can make a graph of how much of each color there is in a given light source.

Burning light sources, like the sun or incandescent lamps, have a lovely smooth spectrum, with an emphasis on the red end:


(Look at the white line in all these images, ignore the dotted line.)

The new warm white LED bulbs also sort of roughly follow the "less blue more red" shape:


But the neon! Look at this:


The spectrum above clearly has too much blue, not enough red and it also has peaks where natural sources don't.

Even though the fixture had a incandescent lamp near the neon it only lifted the red a little bit:


So now I make sure I always buy warm white light bulbs, to avoid general disgruntlement in the home. Our eyes have probably evolved to work best with light which is, well, the same colour as the sun. In the end the light fixture had one warm white led and a surviving incandescent bulb, lifting the red end a bit:



And did the family notice? Did they?! Like hell they did, but they stopped complaining at least.


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