A system for measuring light absorption levels for a liquid for use in a printing system includes a light source adapted to provide a divergent beam of light, a liquid container with a hole that acts as a focusing lens, and a prism disposed over the hole to split the divergent beam of light into a reference beam and a measurement beam. The systems include a measurement detector to measure the intensity of the focused beam to produce a liquid measurement signal. A reference detector measures the intensity of the reference beam for compensating the effects of temperature and light source variations on the system signals. A device calculates signal ratios and stores the ratios so that the signal ratios of subsequent colored liquids can be converted into colorant concentrations from a look-up table or through calculations using a signal ratio/colorant concentration.