Abstract: An improved light intensity measuring device includes a temperature compensating logarithmic amplifier that changes photodetector currents which have been converted from AC to DC to a voltage which drives an analog to digital converter. The resulting digital signals are displayed. For differential or absolute measurements, a second, identical, logarithmic amplifier channel is employed and both are coupled to a differential amplifier. A standard reference current applied to one channel provides an "absolute" measurement of the signal applied to the other channel or a second signal may be compared to the first.