1. Registered User Level 1 Gladiator: Andabatae
Join Date
Jul 2006
Location
Norway
Posts
24

Reflected light\color

I`ve done some experiments to test how color reflects from one surface to another. I sat out in the sun and held different colored materials so that the light reflected from them unto my leg ( of all things, anyway, since my leg is pretty fair(white) the different colors, eg. blue or orange did not change and reflected blue and orange on my leg.

Anyway, the other day I studied an illustration and I noticed that the artist had blue light reflecting on the characters from below. That is - it reflected blue on a piece of metall, but reflected green on one of the characters yellow jacket. So my question is: will a reflected color change according to the color of the material it is reflected onto?

will red reflected light "turn" to orange when reflected on a yellow surface or will it "keep" it`s redness ( if you get what I`m saying).Will green reflected light "grey out" on a red surface or will it still show as green?

I`m in doubt because I know that the color of a dominant light source affects all the colors in a scene, but I haven`t done any experiments yet to test out my question above ( regarding the reflected light).

2. When coloured light bounces off a coloured surface, the balance of wavelengths in the reflected light is determined by subtractive mixing - the reflected light will LACK the wavelengths missing from the light source AND those removed by the coloured surface. Consequently you would expect to see only the wavelengths in common to the two colours.

With subtractive mixing, the result is impossible to predict exactly from the appearance of the component colours - it depends on the actual spectral curve of each. Brown University has some simple applets demonstrating this and other aspects of colour theory. Try the ones on "Reflection" and "Two Materials" - you can vary the colour balance of the light source and coloured surface and see the result as a spectral curve and also (in the second one) as a colour.

Everything I've said so far refers to the main (diffuse) reflection. The highlights (specular reflections) normally retain the colour balance of the light source. The reflection from shiny metals is typically all specular reflection, so unless it's a coloured metal (like copper or gold), the colour should be the same as the light source.

Also, as you correctly note, colour is an experience that is influenced by surroundings, not just the wavelengths of the light itself. To be specific, it will make a difference whether the coloured light is the dominant light, or whether the results are viewed in the context of surroundings lit by white light.

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