| 摘要 |
The invention is directed to a large aperture zoom lens of the improved optical performance, serving as a standard zoom lens especially suitable to a single-lens reflex camera. The zoom lens employs a zooming system with four groups of lenses having positive, negative, positive and positive refractive powers, respectively, and implements on the order 75 degrees of a photographing angle of field at a wide-angle end of the range, approximately 2.8 of F number throughout the zooming range, and about 2.8 of a variable power of magnification while still dimensioned as close as the standard zoom lens for the single-lens reflex camera (i.e., about 95 mm in total lens length and phi67 mm in filter diameter on the side closer to an objective lens).
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