A device for making accurate, reproducible light reflectance measurements on an optically nonuniform specimen comprises means for holding the specimen in a fixed position. In one embodiment the specimen is illuminated by light sources that are arranged at acute angles relative to the specimen and (360.degree./N.+-.1.degree.) apart in azimuth, where N=the total number of light sources. The light sources are sequentially energized and deenergized to illuminate the specimen. A light detector receives light reflecting from the surface and generates an electrical signal, which is subsequently processed. In another embodiment the light sources are arranged in pairs in which the two light sources in a pair are simultaneously energized and deenergized and the pairs are sequentially energized and deenergized. A method for measuring reflected light is also provided. The device and method are useful for making biochemical assays with reagent test strips by measuring the tone of coloration of the strips after treatment with a target substance being examined.