# About the sun and moon **URL:** \ **Category:** Factual Questions\ **Created:** [April 15, 2002, 1:54pm UTC](https://boards.straightdope.com/t/about-the-sun-and-moon/103729 "2002-04-15T13:54:18Z")\ **Posts on this page:** 3\ **Page:** 2
**Author:** ![panamajack](https://avatars.discourse-cdn.com/v4/letter/p/47e85d/32.png) [@panamajack](https://boards.straightdope.com/u/panamajack)\ **Post date:** [April 16, 2002, 8:57pm UTC](https://boards.straightdope.com/t/about-the-sun-and-moon/103729/21 "2002-04-16T20:57:44Z")
Not really related to the topic, but similar to **fs** ’s comments about what we perceive as white; we can also see color even when the light doesn’t come in as we’d expect (this is probably not related to the sun, but I suppose it might be.) Land developed the ‘Retinex’ theory of color (combination of retina & cortex) from experiments. An interesting, if not terribly technically-minded, discussion can be found at[Wendy Carlos’ website](http://www.wendycarlos.com/colorvis/color.html). Searching on ‘retinex’ might reveal more. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [April 16, 2002, 9:15pm UTC](https://boards.straightdope.com/t/about-the-sun-and-moon/103729/22 "2002-04-16T21:15:53Z")
**femtosecond** that was an illustrative and useful link. Thanks for doing some homework for those of us, like myself, who are too lazy to do it. We can see that the color of daylight is far from white, even before being filtered by the atmosphere. \>\> I am baffled about the “different times of the month” comment. **TBA** , as I said above, it was just a joke. That’ll teach me to make jokes. Forget the whole thing. All I wanted to point out was that different stars have different spectrums and there’s no reason to expect them to be any color in particular. (Now someone will pick on me and say the plural of spectrum is spectra). Regarding color perception, the animal eye is possibly the worst sensor because it adapts so easily. As long as the light source is relatively wide in spectrum the eye can easily balance it and see “white” light. Incandescent lightbulbs, daylight and fluorescent lights differ greatly in their spectrum and yet the eye adapts to all easily. OTOH, film is more accurate and you need filters. If you nitice, computer cams have settings for different light sources. In general light sources are grade by “Temperature” and you can see that used to describe light sources. Sunlight has a much lower temperature (more red) than fluorescent light. Also, I believe equal quantities of Red, Green and Blue do not make white as the eye is not equally sensitive to all three colors. Color TV signal does not weigh the equally in the Luminance signal. I hope it is obvious for now that you can get white by mixing three colors but also you can do it with just two and I believe that was used as tha basis for Polaroids (or for something else, my memory fails me) > [@](#): > > from E. Britanicca: > > A series of experiments performed by Edwin H. Land in the 1950s called both theories into question. Land demonstrated that a wide range of colors could be produced from a mixture of only two colors. He photographed the same scene twice—once with light having long wavelengths, and once with light having medium wavelengths. He called the two types of photographs that resulted the long record (for long wavelengths) and the short record. When Land projected the two records onto the same screen—using red light to project the long record and white light to project the short record—the image on the screen seemed to have a full range of colors. Land suggested that some of the colors seen whose wavelengths were absent were perceived through a process involving the comparison of surrounding colors. He surmised that the total combination of colors in a scene played an important part in color vision. His experiments can also be interpreted as proof for the two-stage theory of color vision. (See also Land, Edwin H.) This reminds me of a trick with a disk with only Black and White sectors on it but whan you spin it the eye sees color. Maybe you have seen it. The eye is a _terrible_ judge of color and photo labs and other places which need reliable measurements use densitometers. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [April 16, 2002, 9:47pm UTC](https://boards.straightdope.com/t/about-the-sun-and-moon/103729/23 "2002-04-16T21:47:31Z")
:: Rushing before someone corrects me:: The light of the Sun is _not_ far from white. BTW chech out the chroma diagram at [http://www.siggraph.org/education/materials/HyperGraph/color/color0.htm](http://www.siggraph.org/education/materials/HyperGraph/color/color0.htm) [Previous page](https://boards.straightdope.com/t/about-the-sun-and-moon/103729.md?page=1)