The goal of the imaging engineer has always been to capture with the camera a faithful image of the outside world and present that image in such a way that the observer sees true to life picture. This goal has never been achieved. In fact the best images made today are frail. If this goal were to be achieved, you would need sunglasses to comfortably view an image of a sunlit vista.

You are asking why cameras don’t capture the entire span of radiant energy that created the human visual response. Why does the modern camera only capture three narrow segments that we call the primary light colors which are red, green and blue?

The answer falls in the category of how we see, namely the human visual response. Over the years there have been many theories proposed regarding how humans see color. So far all have failed to give a satisfactory explanation of every aspect of how we see colors. The wave lengths span that our eyes are sensitive to covers the range of 400 to 700 millimicrons. It is no accident that earth’s atmosphere is transparent to this range.

When we stare at a light source, we cannot distinguish any one particular wave length unless it is presented alone. When we look at a white light source, we are unable to isolate and identify any specific color. Our eye/brain combination interprets the color of the light without analyzing what makes up the mix of frequencies. Capitalizing on this, scientists have proven by experimentation that by mixing only three colors in varying proportions, almost all colors can be produced. In other words, presenting to the human eye, in varying intensities, a mix of red, green and blue, most spectrum colors can be reproduced, not exactly but a close approximation. This was the work of Thomas Young (British 1773 – 1829) titled the Young Theory of Color Vision.

Building on Young’s theory, James Clerk Maxwell (British 1831 – 1879), showed the world the first color picture photography produced. In 1855 he used three projectors and superimposed the three images projected on a single screen. Each projector was fitted with a colored filter. The three images were each one of the three light primary colors, namely, red, green, and blue. The film images projected were made by taking three separate pictures on three pieces of black and white film, each exposed thru one filter of the three light premiers.

Since that day in 1855, innumerable methods to make and display color pictures have been explored. Early color motion pictures projected feeble color images using just two colors. Edwin Land (American 1909 – 1991) founder of Polaroid Corp. experimented making color pictures using only two primary colors. This has remained a laboratory curiosity. So far, the most faithful color images are made using the three color primaries. However, one man, Gabbriel Lippmann (French 1845 – 1921) made beautiful color images that captured the entire visual light spectrum. He devised a method that employed black and white film with a mirror backing. The exposing light penetrated the film, hit the mirror and was reflected back into the film. Thus the exposure was made via two transits of the exposing light. The image comprised of silver arranged with a spacing equal to the wave length of the exposing light. When viewed, the film only allowed light to pass that matched the wave lengths of the exposing light. One could behold a full color picture that contained no dye of pigment. Unique and beautiful, the Lippmann process remains impractical. Our film and digital cameras fall back to the method used by Maxwell. Perhaps, if you study human vision and color theory, maybe you will be the one that advances our science and obtain the first truly faithful image.