| 摘要 |
PURPOSE:To automatically obtain suitable exposure by detecting that the rate for a dark part where a video signal comes to be under a constant value to occupy in the whole screen is larger than a value and discriminating backlight condition. CONSTITUTION:A comparing means 10 to compare the output signal of a signal processing means 5 and a reference voltage Vd determined in advance and to output a signal when the output signal of the signal processing means is less than the reference voltage and an integrating means 11 to integrate the output signal of the comparing means 10 and to detect the rate the output signal of the comparing means is generated in a constant time are equipped and when the integrated result is larger than a constant value Vdref determined in advance, it is detected that a photographing condition is a backlight. Thus, since the rate a dark part where the level of the video signal is smaller than a constant value occupies in a screen is detected and a backlight condition is automatically discriminated, a video camera to surely adjust light quantity without fail can be constituted.
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