| 摘要 |
PROBLEM TO BE SOLVED: To enlarge a lens usable extent and to eliminate a lens exchanging work by arranging a non-standardized open end for attaining a diaphragm aperture larger than the open end of a diaphragm capable of securing a prescribed optical performance suitable to high image quality photographing, and making it possible to switch the position of the open end in accordance with the situation. SOLUTION: As for the lens device used for a high-definition television system camera, the lens device is provided with two photographing modes; a mode A for attaining the prescribed optical performance suitable to high vision photographing and a mode B by which the prescribed optical performance of the mode A cannot be secured in terms of performance, but which includes the using extent of the mode A, and also,, capable of photographing in a lower luminance area. As for the open end of the diaphragm in the mode B, the diaphragm aperture diameter is set larger than that of the open end of the mode A, and then, the mode A is selected in the case the sufficient light quantity is secured, on the other hand, in the case the sufficient light quantity is not secured, photographing is performed after selecting the mode B. It is allowed to switch the position of the diaphragm open end by a mechanical means or by an electrical means.
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