Abstract: A color analyzer simultaneously responsive to light intensity at multiple wavelength regions emitted by or reflected from a specimen illuminated by existing ambient light for instantaneously determining relative ratios of the wavelength regions comprising a plurality of interchangeable photodetectors having different spectral response characteristics; a separate optical probe for each photodetector for imaging the light emitted by or reflected from the specimen onto its associated photodetector, the optical probes having identical dimensions and imaging characteristics and being arranged in side-by-side, parallel relationship in order to permit each optical probe to be affected equally by ambient light changes; and means responsive to the outputs of the photodetectors for rationing such outputs and providing the resultant ratio signals for utilization. Also disclosed is a closed loop feedback system to permit the individual ratios of any or all of the photodetectors to be monitored simultaneously.