1. A method comprising, in combination: (a) using an imaging sensor to take measurements of light from a first scene, which light has, after leaving the first scene, passed through or been reflected from a SLM; and (b) using one or more computer processors to use the measurements of the light as inputs to perform calculations to compute a first light field function of the light; wherein the calculations include multiplying a light field dictionary matrix or multiplying a light field atom in the light field dictionary matrix, which light field dictionary matrix has, before the imaging sensor takes the measurements, been computed from training sets, which training sets comprise or were extracted from light field functions of light from other scenes, the first scene being at least partially different in appearance than the other scenes.