| 摘要 |
PROBLEM TO BE SOLVED: To prevent the vignetting of luminous flux on the periphery of an image plane and further to obtain a sufficient telephone effect even in a high- vision broadcasting system in a state where a lens for aspect ratio 4:3 is used as it is by inserting an extender having about 1.2 power in the relay lens part of a zoom lens and shifting a focal length to a long focus side. SOLUTION: When general image pickup corresponding to the aspect ratio 4:3 is performed, an auxiliary lens group 4 is retreated from space on an optical axis X. Meanwhile, when image pickup for a high-vision broadcasting system corresponding to the aspect ratio 16:9 is performed, the lens group 4 of an enlarging system is inserted in space on an optical axis X and further the lens group 4 is constituted. When it is assumed that the focal length of a positive front group and a negative rear group are f1 and f2, the lens satisfies an expression: -1.3<f1/f2<-1.1.
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