1. A method of fitting a visual prosthesis, comprising: applying a plurality of stimuli to visual neural tissue; measuring brightness responses to said stimuli by sensing patient responses including a threshold of perception and any two additional points; deriving a formula based upon said brightness responses to said threshold and said any two additional points, comprising a stimulation curve estimating brightness levels not tested, said formula being derived starting from empirical data, said threshold of perception and said brightness response to said two additional point and corresponding to a curve fitting of the empirical data; and generating said stimuli by applying said formula to visual input.