1. A method for determining a gamma curve parameter for a gamma curve function for converting a digital signal produced by an optical sensor from a nonstandard color space to a standard color space, the method comprising: minimizing a joint quality metric comprising: a color portion based on a relationship, within a uniform perceptual color space, between an gamma curve compensated signal and a standardized signal for a reference source, the gamma curve compensated signal derived by applying the gamma curve function to a digital reference signal captured by the optical sensor for the reference source; a noise portion based a noise level of the gamma curve adjusted signal; and a contrast portion based on a contrast of the gamma curve adjusted signal.