Precision and Accuracy of Spectrophotometric Reflectance Measurements

The Inter-Society Color Council has made a study (1) of the reproducibility within a given laboratory of the General Electric recording spectrophotometer, and the variability of different instruments from one laboratory to another. The samples used as standards were ten Carrara glass plaques from Pittsburgh Plate and four colored acrylic plaques from Du Pont. A different study (2) compared a General Electric instrument and a Bausch & Lomb Spectronic 505 within the same laboratory. The consitions under which the studies were carried out will be discussed, as will the results. Both studies were concerned with transmittance as well as reflectance measurements. Only reflectance will be discussed, except to mention that in all cases the variations in reflectance measurements exceeded those for transmittance.