PURPOSE: To achieve the higher speed of calculation by storing the value of exposure time TV corresponding to the preprogrammed exposure value EV, calculating TV from the digital signal of the exposure value EV obtained from said data and photometry results and calculating AV from EV and TV.

CONSTITUTION: The exposure value EV corresponding to the subject luminance is outputted in digital signals of 8 bits from the circuit 1 and the address of a permanent memory ROM 7 is assigned by the address signal based on the signal of the upper bits thereof. The value of the exposure time TV corresponding to the exposure value EV having programmed beforehand has been stored in that address and the exposure time TV is calculated in an adder 8 from the data thereof and the signal based on the lower bit of the exposure value EV. In a subtractor 9, the aperture value AV is calculated from the EV and TV value and is outputted to a display and exposure control circuit 10.