| 摘要 |
PURPOSE:To suppress overexposure in short distance photographing by increasing a dimming comparing voltage in accordance wit time and advancing a dimming signal generating time in accordance with the quantity of light received by a photoelectric conversion circuit. CONSTITUTION:When the quantity of reflected light from a subject is abundant in comparatively short distance photographing, an output from a photoelectric conversion element PD which is proportional to the quantity of light is integrated by an integrating circuit constituted of an amplifier A2 and a capacitor C on the basis of an output from a synchronizing switch for emitting a flash tube 3 and outputted to an amplifier A4 as an integrated voltage Vc having a sharp inclination. The amplifier A4 compares the voltage Vc with a dimming comparing voltage Vth outputted from the final stage TR TR4 in a comparing signal generating circuit for amplifying the output of a DA conversion circuit 2, and when the voltage Vc exceeds the voltage Vth, outputs a dimming signal from a terminal TM7 to stop the succeeding operation of a CPU1. When the quantity of reflected light is excessive and the rising gradation of the voltage Vc is sharp, the generating time of the dimming signal is advanced to suppress excessive exposure. |
