“What is color? No object of itself alone has color. We know that even the most brightly colored object, if taken into total darkness, loses its color. Therefore, if an object is dependent upon light for color, color must be a property of light. And so it is.” Paul Outerbridge, Photographer 1896 – 1958
As Mr. Outerbridge so succinctly states, color is a property of light…or, otherwise put, a function of light. Color and light are intrinsically entwined…part and parcel of each other… mystic twins, or co-dependents, depending on your point of view.
Sunlight, or white light, is the combination of the entire electromagnetic spectrum ( a light source’s spectrum is a distribution giving its intensity at each wavelength, and most light sources emit light at many different wavelengths)..in essence, all the colors of the rainbow. Their combination creates white light, while lack of light, no color, is perceived by us as black. Though artists may see black as a color, it is actually the lack of color: a state of no color. We are discussing color, and color mixing from the point of view of light wavelengths, not color mixing as regards to paints. This is physics…the physics of light and color.
The terms “color” and “wavelength” here may confusing. Our eyes will perceive the color based on not only the wavelengths of light that the object we are viewing reflects or absorbs, but also on the actual measurement of those wavelengths…measured in nanometers. We can see the reflected colors of light which lay in a very small region of the electromagnetic spectrum called, aptly enough, “visible light”. We cannot see color wavelengths that are absorbed by an object or surface.
Wavelengths ranging from about 400-750 nanometers make up the visible spectrum of light that can be perceived by the human eye. When light strikes an object certain of its wavelengths are absorbed by that object, and others are not. Those that are not, those wavelengths of light which bounce or are reflected off an object, are perceived by the human eye as color. In essence, “An object appears a certain color because it reflects certain light wavelengths, which are then perceived by the eye.” –http://www.wisegeek.com/what-is-the-color-rendering-index.htm
Surfaces we see as black absorb all of the wavelengths of light in the visible spectrum which reach them. All the “color” thus is absorbed, and we see no color, and thus black. Surfaces we see as white are reflecting, or bouncing back to our eyes, (specifically, the rods and cones -photoreceptor cells- within our eyes), all of the wavelengths of visible light which reach them. Thus, as all of these visible wavelengths are being reflected “to us”, and their combination, as discussed above, creates white light, as white light (discussed above) is the combination of entire electromagnetic spectrum, or all the colors of the rainbow! (Mind you, if you mix a wide spectrum of varying paint colors together, you will not get white! We are discussing color in reference to light only in this post!).
Each light source emits different wavelengths of light, thus the way we perceive colors varies depending on how the object we are seeing is illuminated, I.E., the wavelengths of light it absorbs and reflects.
Ah..now we begin to get to the heart of the story…the Color Rendering Index, or CRI. It will take a second post on this complex subject to further demystify it.
“The Color Rendering Index is an international measurement scale that describes how colors are rendered under an artificial source of light. The standard against which artificial lighting is compared is daylight, because daylight renders the widest variety of colors. Artificial lighting, by contrast, can render very many or very few colors, depending on the nature of the light source. The color rendering index has many applications, especially in art and photography.” –http://www.wisegeek.com/what-is-the-color-rendering-index.htm
“The Color Rendering Index (sometimes called color rendition index), is a quantitative measure of the ability of a light source to reproduce the colors of various objects faithfully in comparison with an ideal or natural light source. Light sources with a high CRI are desirable in color-critical applications such as photography and cinematography. It is defined by the International Commission on Illumination as follows:
Color rendering: Effect of an illuminant on the color appearance of objects by conscious or subconscious comparison with their color appearance under a reference illuminant.
The CRI of a light source does not indicate the apparent color of the light source; that information is under the rubric of the correlated color temperature (CCT).” –http://en.wikipedia.org/wiki/Color_rendering_index
Because of the complexity and relative “thickness” of this subject, I will delve further into the Color Rendering Index, Color Rendering itself, The International Commission on Illumination, and Correlated Color Temperature, in a subsequent post.
Until then…I am wishing you much light and color in your life. May your spirit be illuminated, and your soul rendered…in all the colors of the rainbow!