A method and apparatus for a single densitometer design that is used for all colors within multiple color image processing system. The preferred embodiment employs an LED having a light adjustment mechanism for controlling the amount of light received by a light detector in the densitometer. The coarse light adjustment is provided through a variable aperture. Fine light adjustment is accomplished through controlling the current through the LED, either by a potentiometer or through an automated process. Preferably, each of the LEDs is selected by wavelength to maximize the absorption by the colorant yielding light roughly complimentary to the colorant. The adjustment circuit provides advantage in color printing systems by allowing duplicate versions of the same densitometer circuit to yield similar voltage outputs for different colorants, thereby compensating for different absorption characteristics and light output of different colored LEDs.