Light field photography is a new imaging technology with a patterned mask inserted between lens and sensor in a conventional camera.The mask attenuates the incident light rays and the sensor records both 2D spatial and 2D directional information.Sharp images at different depths could be calculated from reconstructed 4D light field.This paper establishes computer modeling of light field camera,and proposes a method of reducing computational amount due to sampling theorem on the premise of image quality assurance.It is proved in the computer simulation.