> How about sunlight? Is that yellow too? (I mean, by the time it reaches 
> the ground.)

It's really difficult to say, as everything to do with "white" is relative 
and your brain does a really good job of filtering out changes in white 
balance of your environment.

Here's a chart I found detailing the sunlight spectrum:

http://org.ntnu.no/solarcells/pics/chap2/Solar_Spectrum.png

You tell me if that's "yellow" or not :-)

> Heh. The trouble is the light in my room ("energy saving bulb") gives off 
> such a pinky yellowy colour that I can't actually tell whether an item of 
> clothing is blue or black. :-P

That's not so much to do with the absolute colour of the white light, but 
with the spectrum.  If you have two monochromatic light sources from a 
yellowy-red laser and a blue laser you can make white light.  THe problem is 
when you try to illuminate something with that white light, the only thing 
you will see is how well the object reflects those particular two laser 
wavelengths.  On the other hand, white light from a black body gives you a 
much better impression of the "colour" of an object because it consists of 
visible light from all wavelengths.  There's a thing called "colour 
rendering index" (CRI) that describes this quality of white light.

Post a reply to this message