1. A method for determining an inverse response function of a camera, the method comprising: finding a first pixel in an output image of the camera in which the first pixel images a first region having a first color and a second region having a second color, the first pixel representing a blended color derived from the first and second colors, wherein the first and second colors serve as component colors of the blended color; obtaining the camera's measurements of the first and second colors; obtaining the camera's measurement of the blended color; and finding a function that maps the measurements of the first, second and blended colors into a linear distribution in a color space.