| 摘要 |
PURPOSE:To set a lens aperture mechanism in the best state for the brightness of a subject, by optionally turning on and off a circuit successding a peak value rectifying circuit through a changeover switching means. CONSTITUTION:When a subject with uniform brightness is shot while a changeover switch SW is turned off, the 1st reference voltage adequate to obtain a rated output signal is applied to video output terminal 3 from a reference voltage generating circuit 11 to control the opening and closing of a lens aperture through a driving circuit 6. On the other hand, when the subject has a high- brightness part nearly in the half part, the changeover switch SW is turned on. Consequently, a video output signal is processed by peak value rectification and amplification, and then inverted by an inverting circuit 9, so a reference voltage applied to a comparing operational amplifying circuit 5 varies in proportion to the high-brightness part of the subject. Therefore, a video output signal free of deficiency of gradations of a shadow part appears at a video signal output terminal 3. |
