In a photometric circuit a reference current is supplied into the input of the logarithmic amplifier at the same time the signal compensating the error originating in the photocell is supplied to the circuit. The reference current corresponds to the current which would occur in the photocell for the lowest measurable intensity of illumination. A sum-and-difference amplifier has one of its inputs supplied by the output of the logarithmic amplifier and its second input is supplied by a reference voltage. The control loop contains a storage capacitor connected after the sum-and-difference amplifier and an impedance converter connected after the storage capacitor. The compensating and reference currents are controlled by switches synchronized with a light chopper mounted in front of the photocell.