Instruments for measuring color, namely spectrophotometers, colorimeters, and densitometers; light integrating spheres; electronic apparatus for measuring and testing the optical and electrical characteristics of light-emitting diodes (LED's); instruments for measuring light, namely, photometers, radiometers, reflectometers, spectroreflectometers, luxmeters, luminance meters, goniophotometers and retrometers; spectrophotometers used for matching paint; electronic apparatus and software for acquiring and assessing tooth color and image information; densitometers for measuring the transmission density and reflection density of both black-and-white and color film transparencies and prints for use in the graphic arts and in medical, photography, and general industrial applications; electrolytic silver recovery units; instruments for measuring image quality; computer software in the field of measuring, analyzing, processing, formulating, and communicating light and color measurement data; computer software in the field of measuring and analyzing the quality of printed and imaged substrates