| 摘要 |
A camera with a zoom lens for keeping in focus at a moving (proceeeding to or receding from the lens) object while the lens is zoomed and the magnification of the object is maintained constant. In the process, at every focal length of the zoom lens, the focusing lens group is shifted from a predetermined position (in an embodiment, it is the position of the focusing lens group where an object at infinity is focused on the film surface) by a distance Cx beta , where C is a constant and beta is the maintained magnification. The constant C depends on the lens configuration; two examples are shown in the description of the embodiments.
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