1. A method of calibrating a cathode ray tube comprising: initializing a lookup table (LUT); adjusting settings of the cathode ray tube to substantially achieve a defined output; measuring output for a number of color values; choosing adjustable parameter values for a device model, wherein a number of adjustable parameters is less than a number of measured outputs; generating entries for the LUT based on the device model; wherein measuring output includes displaying a substantially white trace during measurement to bias an output measurement; and wherein the trace has a halo shape.