| 摘要 |
PURPOSE:To obtain uniformly gradation with fidelity by comparing a mean brightness detecting signal of an image pickup picture obtained by a vidicon with a mean brightness signal at the middle part. CONSTITUTION:A photoelectric converting element 9 arranged at a focus of a lens 7 of a short focal point detects the entire mean brightness of an image pickup picture obtained by the vidicon 2. The mean brightness of the middle part of the image pickup picture obtained by the vidicon 2 is detected by using the photoelectric converting element arranged at the focus of a long focal point lens 8. The detection signal of both the photoelectric converting elements 9, 10 is inputted to a comparison circuit 11, where they are compared and a semiconductor switch 6 is controlled based on the result, correction circuits 4A, 4B are selected and gamma correction is applied properly to a luminance signal at image pickup at the condition of back light.
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