16,000,000 colors are not enough!
This article explains why the 16,000,000 colors of your latest graphics board / color LCD monitor are not enough. Here is the main crunch: 16,000,000 colors does not necessarily mean all the colors the eye can see. In fact on computer screens and color printers, the 16 million colors are squashed into a more limited range than the eye can percieve. Estimates vary, but the eye can probably, at most, distinguish 10 million colors. But the range of these colors is greater than the range of technology. It is like going to a restaurant which has a list of meals, all the same, but each with one more grain of salt in the sauce. It is different, but indistiguishably different!
Here is a graphical representation of the statement that the 16,000,000 colors of your monitor are all squashed into the center of our visible range:
The above diagram represents all the hues (spectral colors) a human eye can see as the area within the red line. Note that this includes the white area within the red line as well as the colorful trinagle. The hues which a given technology (printer or monitor etc) can reproduce are inside a triangle, which is smaller than the area of the red line. So though we have 16 million colors, none of them can represent the colors outside the triangle.
The red line itself represents the pure spectral colors. The colours you would see in a particularly pure and vibrant rainbow. As you can see the color triangle approaches the line at its corners, but never realy touches it.
Each device (monitor, printer, projector, whatever) will have a different color triangle. Here is a color triangle of a different device:
Comparing the the two triangles you can say that the device represented by the first triangle has a wider range of color than the one represented by the second triangle.
And don't confuse the colors you see in these images with the colors in the real world. This is just a technical representation, useful to manufacturers, engineers and scientists. (I have removed many of the numbers and annotations from the diagrams to simplify this explanation.) I could have shown the two diagrams in black and white, it would not have changed the information content.
Images are great for conveying ideas, and here is another version of what I explained above:
One last word, you can disrupt the "realism of color" simply by changing the contrast or brightness on your monitor, or closing the curtains on a sunny day, or switching off the light at night. Color realism is a slippery animal, and "True Color" is probably a species of unicorn. If you think you've seen one you probably haven't.