The Math Behind the Forced Perspective Optical Illusion In Which Objects Appear to Change in Size

In an interesting technical tutorial Filmmaker IQ, host John P. Hess explained the specific formulas used to calculate the forced perspective illusion, a camera technique that uses distance to make subjects appear larger or smaller than they actually are.

** ERRATA ** at 2:49, it should be width divided by the distance…It’s one of the oldest tricks in the book for making things appear larger or smaller than they really are. In this lab we will break down the actual science and math behind forced perspective and demonstrate by putting a model in a martini glass.