| 摘要 |
PURPOSE:To obtain proper exposure even when an object is on rear-light condition by measuring luminance at the center part and circumferential part of a scene and varying a dimming level in daylight synchronized photography according to their luminance difference. CONSTITUTION:Luminance signals corresponding to the center and circumferential part of a scene measured by photodetecting elements 1 and 2 are inputted to a differential amplifier 7 through operational amplifiers 3 and 4. Its difference output is inputted to a switch 17 through the diode 15 of a minimum value setting circuit and a buffer circuit 16. The averaged photometric value of a photodetecting element 22 is compared with a constant voltage determined by resistances 25 and 26 by a comparator 21, which outputs a signal for selecting a switch 17; a dimming level signal is led out of the circuit 16 in daylight synchronized photography as a substitute for a constant voltage determined by resistances 18 and 19 and compared with the output of the flash discharge tube 30 of a PT 28 by a comparator 20. When they become equal to each other, a emission control circuit 32 stops powering on the discharge tube 30 to obtain proper exposure. |
