On-Line Measurement of Color - Densitometer or Spectrophotometer?

Discussions about the on-line color measurement of a print often deals with the question of whether a densitometer or spectrophotometer should be used. The question relates to the number of channels needed to measure the reflectance properties of a print, arising from the fact that, the reproduction of color in printing is affected not only by the light absorption properties and the amount of the inks but also by a number of other factors. Consequently, in four-color printing the four channels of a densitometer might not be sufficient to measure the reflectance properties of the print.