Camera Angle Projection is a way to convert a blueprint to a perspective drawing or the reverse: taking a photo and extracting a blueprint. This was a standard skill for Hollywood art directors, set designers and storyboard artists. Harold Michelson devised the method below. He was long considered the most knowledgable artist in this technique in Hollywood. Today the computer can provide the same functionality, but much faster of course. Still, CAP is one aspect of perspective and lenses and provides insights into drawing for film that is worth knowing.