Recent developments in image technology have significantly expanded the range of existing pictorial mediums. Painting, photography and film have been joined by video games, holograms and augmented reality, while newer technologies keep appearing. Given this growing variety of new mediums, what does the term medium even mean today? Is it possible to categorize them into a systematic typology of pictorial mediums? This article approaches these issues by reconsidering the meaning of medium. It builds on Leon Battista Alberti’s metaphor of a painting as a window to another world and explores what types of windows there might be.