Geometric construction of relativistic and non-relativistic distortion

To an observer moving through a scene with a relativistic velocity, the scene appears distorted. Here we present a simple geometric interpretation of this relativistic distortion. This interpretation is exact for pinhole cameras whose shutter coincides with the pinhole, and it can easily be modified to take into account time-of-flight effects only that lead to a "non-relativistic distortion", allowing a separation of the relativistic distortion into time-of-flight effects and "truly relativistic" effects. We make use of our construction in Einstagram, a web app designed for running on mobile devices that displays the video streams from the device cameras, relativistically or non-relativistically distorted for an arbitrary, user-defined, observer velocity. Our work facilitates an intuitive understanding of relativistic distortion.