A scanner records a film's color by recording the image through red, green, and blue filters. Recording it in ultraviolet or infrared or other nonvisible wavelenths would produce different images. In true tricolor photography or digital imaging, three grayscale images of an object are made using red, green, and blue filters. The grayscale images are composited, either in the darkroom or digitally, to create a color image. Classic tricolor photography is far more useful for science than my synthesizing technique because the bandpass of each tricolor filter is known.
Astronomers find negative images easier to work with.
The image below is the inverted blue channel of the posterized image above. The extent of the tails is much more visible. Copyright 1998, James R. Conner, all rights reserved.