Focal Distance and the Pinhole Effect: Clues to the Mystery of the Apparent Size of Things

Abstract

This article traces an ergonomics research odyssey that spanned more than half a century. It started in 1950 with an airplane equipped with a periscope that projected a forward-looking view on a screen above the instrument panel and ended with a partial explanation for the illusion of a shrinking moon as it rises from the horizon. The connecting links along the way are not easy to follow and fly in the face of current theory, but the experimental findings tie the apparent size of visible objects to the focal distance of the eyes. The findings also have practical applications to the design of imaging displays and virtual reality systems.