ABSTRACTThe application of spectral sensitivity measurements to clinical problems has been limited by the complexity of calculating the corrections for nonlinearity and non-neutrality of the neutral wedge and for the quantum intensity of the test beam. A simple electronic system is described which performs all these calculations automatically, as the subject makes the sensitivity setting, and records the sensitivity on an XYplotter. A range of 5 log units is covered with an accuracy of 0.05 log units.