reference plane, <in photometric or radiometric measurements>
plane in which the surface of a sample or standard is placed during measurements
Note 1 to entry: For reflection measurements, the geometry is defined with respect to the reference plane. For transmission measurements, there is a reference plane for the incident light and a second reference plane, displaced by the sample thickness, for the transmitted light.
Note 2 to entry: This entry was numbered 17-1055 in CIE S 017:2011.