| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a large-diameter lens that decreases aberration change resulting from focusing, uses an inner focus system, copes with brightness with approximately 1.4 of open F value, and has a high performance, while decreasing the weight of a focus lens in order to cope with automatic focusing in moving picture photographing, despite a simple configuration. <P>SOLUTION: The large-diameter lens comprises, in order from an object side, a first lens group G1 of positive refractive power, a second lens group G2 of negative refractive power, and a third lens group G3 of positive refractive power. An aperture diaphragm is disposed between the first and second lens groups G1 and G2, and a focusing takes place by moving the second lens group G2 toward an image surface side. Such a large-diameter lens satisfies predetermined conditional expressions. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
