What can I do if my sample is not uniform?

It must be realised that a spectrophotometer (or a colorimeter) spatially averages the light reflected by a sample: thus it is possible that a uniform grey sample and a black-and-white checkerboard sample could give rise to identical measurements. The CIE system is strictly limited to the measurement of uniform colour stimuli.

Digital colour camera devices are beginning to be used for colour measurement - especially for textured samples. They measure colour at many thousands of spatial locations on the sample but currently provide relatively poor colour resolution and precision.