| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and a lens enabling a camera to record desired coincident spatial frequency response all over the range of focusing. SOLUTION: The method and the lens system for changing the modulation transfer function of light passing through the lens system of the camera or other image system by providing a filter (SFMR) for changing the spatial frequency response in the lens system are obtained. The SFMR filter is a thin film or other type modulation filter including the conventional optional diffusion filter. The SFMR filter is provided at such a position along an optical axis that the in-axis light of the angle of visibility being zero becomes parallel in any lens system and forms luminous flux having substantially constant cross-sectional area all over the range of focusing of a principal lens or all over the area of the zooming and the focusing of an objective zoom lens, and gives the coincident modulation transfer function of the light reaching the camera or other image system.
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