Here is a page from a photography class notebook of Draper’s, circa 1968. He is practicing planning what his shutter speed and aperture settings should be for each area of a potential photograph. The approximation gets based on the reflective qualities of the materials in the scene and the shadows being cast onto each area. Draper has notated each possible surface with the required shutter speed and aperture setting. He then could pinpoint an average setting for the entire photograph.