In the 1970s, I remember my then father-in-law, a professional photographer, saying about a stunning (for its time) Kodak TV commercial which we were watching, manipulating moving images within moving images, that he had seen it being produced but that he had been enjoined not to reveal the trade secrets behind it. It dawned on me later that this must have been an early escape from the big film studios of what has become known as Chroma key. It was the invention of Petro Vlahos who has just died. He saw the possibility of replacing the complicated physical matte shot, which often necessitated skilled scenery painters, with something more reliable and capable of producing more spectacular effects. The use of blue screen and green screen was developed by his company and aided by the exponential growth in power and memory density of computers. Now the basic technique is available to anyone with a digital camera and a PC with a graphics processor, but we should not forget the original intellectual breakthrough from the days of celluloid.