Color and Light in Digital Photography: Digital Cameras Basic Theories

Reproducing images "as we see them", in color, is an ambition much older than photography. Color vision is something of our nature; but, the complexity of this sense and of photographic color reproduction is huge. Contrary to what one may think, color photography is not only an "objective" reproduction of reality. The fact of framing and choosing a scene with determined colors has important consequences in the image. Colors can give all kinds of information, can harmonize or unbalance, and with a camera in hand cam be used selectively to describe an important part of the things we want to say in a photograph. Color film is more demanding than black and white. Also, color is much more difficult to control than the different densities of gray. In exchange of these difficulties, a good color picture, were the technical medium has been used to have the tones appear in the image in the desired way, stands out from the uncountable photographs were color has been left to a simple cause-effect relationship.

Light and Color
We call all radiation that is visible to the human eye, light. Light is an electromagnetic phenomenon. Light radiations are characterized by a movement in a straight line at an enormous speed (300,000 km/second in a vacuum) and, simultaneously, by and waving movement on all planes. This characteristic wave movement is similar to that of any other electromagnetic radiation, as in radio

waves. What characterizes any wave phenomenon is the wavelength (distance between two consecutive crests of the wave). The different wavelengths of light cause different nervous stimulus in the retina, which give way to color sensation in the brain. Radiation with a wavelength between 7,000 ¿? (angstrom, or ten millionth of a millimeter) and 4,000 ¿? Constitutes the range of visible color or visible spectrum . The top limit (7,000 ¿?) corresponds to red; afterwards there are infrared radiations which are invisible to man; on the bottom limit (4,000 ¿?) corresponds to violet, and lower are ultraviolet radiations. Between both extremes we find the different colors of the spectrum, those of the rainbow. The composition or spectrum of any kind of light is the range of colors in it.

What we call white light is a mix of all it's wavelengths. When white light comes in contact with a object, it absorbs part of the spectrum and reflects (dull objects) or transmits (translucent or transparent objects) a determined range of wavelengths that make up it's color .

If a surface reflects all colors equally, in the same proportion, we say that the object is white or gray. If it reflects some colors and absorbs others, the object will be colored. An object that lets through, or transmits only determined wavelengths, filters white light changing it's composition.

Therefore, we can consider color as light ( color-light ):

• As a result of a combination, of the sum of colors (wavelengths) in determined proportions (composition of emitted, reflected or transmitted light).
• Or also, as the result of subtracting from white light a determined part of the visible spectrum (the colors that are absorbed or retained by a surface or filter).