1. A method comprising: storing, in a data storage device, a look-up table representative of a tone reproduction curve for a print engine, said look-up table correlating target values for a color to be printed by said print engine with digital input values; generating, by said print engine and based on a selected digital input value, a test image having said color; determining, by a processor, a difference between an actual value of said color and a corresponding target value for said color, said corresponding target value being correlated in said look-up table with said selected digital input value; and updating, by said processor, said look-up table so that said corresponding target value for said color is correlated in said look-up table with an adjusted digital input value that corrects for said difference, said updating comprising making a series of incremental adjustments to said selected digital input value.