The study of shadows—Kepler’s ‘light figures’ and pinhole imaging

Kepler’s theory on pinhole camera imaging is still valid today, its development is well documented and provides an exciting context for optics lessons. Kepler presented a generalised concept of ‘light figures,’ describing the formation of soft shadow images through the interaction between extended apertures and extended light sources. The work marks the culmination of Kepler’s extensive engagement with the ‘Moon Puzzle.’ In this paper, we examine Kepler’s theory and depiction of ‘light figures’ from both historical and experimental perspectives. We provide an overview of Kepler’s theory and its historical context, and present experiments that illustrate Kepler’s theoretical insights, specifically designed for educational use. In this way, a generalised concept of soft shadow imaging can be integrated into optics education, drawing on an authentic historical context.