“A true science of data visualizations requires both a theory of perception and of computer graphics. However, visualization designers have paid relatively little attention to perceptual issues. In this article, I outline how knowledge of human visual perception and physiology can lead to more effective visualizations. Bertin’s (1983) Image Theory, the only comprehensive perceptual theory in the visualization literature, will serve as the medium for the discussion. Experimental vision research grounds Image Theory in ‘first-principles’ and suggests corrections, modifications and extensions. The resulting updated version of Image Theory can serve as a guide to visualization design.”