The perceived color of a sample depends on the angle of the incedent light on hte sample and on the angle from which the sample is observed. This measurement geometry must also be taken into account and defined in the measurement techniques and in the spectrophotometers used. We talk of the measurement geometry used in the spectrophotometer.

In spectrophotometry, a disctinction is made chiefly between diffuse lighting (d) produced by a flash lamp illuminating an integrating sphere and lighting directed at a specific angle (e.g. 0 degree or 45 degree).

The reflection is always measured at a specific angle of observation - 0 degree, 8 degree or 45 degree. Various measurement geometies have been developed for different applications. In the paper industry, a d/0 degree measurement geometry is used, whereas in the textile and plactics industry, d/8 degree is used. The graphic arts industry prefer 0/45 or 45/0 degree.