To analyze appearance attributes optically, one first separates the chromatic attributes from the geometric ones. The chromatic, or color, attributes may be represented in a variety of forms which start with the purely physical spectrophotometric curves. By incorporating the sensory processes of the human observer, one converts spectrophotometric data to colorimetric specification by use of the CIE Standard Observer and Coordinate System. To obtain analyses which relate closely to the observer's sensory impressions, one can convert CIE specifications to one of several opponent-colors (L,a,b-type) analyses or to hue, value, and chroma of the Munsell-type analyses. These sensory-related color specification systems can be used to locate points representing colors in three-dimensional coordinate systems. Geometric attributes are those related to the geometric manners in which objects and materials distribute light and are known by terms such as gloss, turbidity, texture, and the like. Measurement methods for many of the various geometric attributes have been developed.

Total instrumental analyses of the physical correlates of appearance are so complex that measurement is not feasible and is never attempted. There do exist, however, a large number of practical, useful methods for instrumentally measuring specific attributes of the appearance of materials. Many of these have been standardized in print by the American Society for Testing and Materials (ASTM), which now has the largest published collection of appearance analyses in existence. Although ASTM has accomplished much in promoting measurements of appearance attributes, there exist important requirements for test procedures not yet prepared. The technical state of the art has recently progressed so that ASTM should now be able to meet these unsatisfied requirements.