Perspective is a rich area for mathematical work, and one that should be accessible to many students, since it is based on the everyday experience of viewing the 3D world directly and through familiar 2D representations (drawings, photographs, images on a television or cinema screen, etc). A nice feature of perspective tasks is that they can be approached in a variety of ways. For example, one can take a very practical "ray tracing" approach of viewing a scene through an appropriate screen and attempting to draw what one sees directly onto the screen. One could also attempt to sketch (and test) the image by using visualisation, or by adopting a more precise "analytic" approach, perhaps involving a plan and side-elevation of the scene and then locating the position of individual image-points on the picture plane--by scale drawing or by computational methods. One way to give "purpose" to this work is to focus on stereograms; i.e., pairs of 2D images which when viewed together produce an illusion of depth. In this article, the author describes how stereograms allow students to take the everyday act of seeing and analyse it in mathematical ways. (Contains 10 figures and 7 notes.)