In the past, where infrared images are often hand painted to give a "quasi-natural colors." Here is an excerpt from the "Leica Manual" by Morgan and Lester (1943): "a very interesting application of infra-red to landscape photography is to enlarge the photo and enlarged tones of blue. If properly organized and fast image will show a white cloud against blue sky, white trees and grass, and various gray to buildings and roads. The addition of oil coloring of trees and grass and other parts of the image will produce a good imitation of a startling natural color. "
