An audience response system in which each audience member is provided with a reflective device (44) (or other radiation source) which is, for example, green on one side and red on the other side. Light from a spotlight (40) is reflected from the reflectors (44) and imaged by a conventional video camera (24). A computer (14) receives the digitized and processed image, forms a map of the audience, and distinguishes the red from the green reflections. This data is then used by the computer (14) to project an image onto a screen (34) visible to the audience, the image being controlled by the red or green image reflections. The audience thus jointly controls the screen image, for instance for purposes of voting or playing a game. The system also can detect movement (direction and/or velocity) of each radiation source which data is aggregated and thereby manipulates the screen image. Also, the sources each may transmit coded information (such as Morse code or ASCII) to individually identify themselves.