| 摘要 |
PURPOSE:To enable simple constituion to perform exposure compensation which accompanies variation in the F number of a lens with the same aperture during focal length switching, by providing an adjusting method for the quantity of transmitted light together with a subordinate lens system in one body. CONSTITUTION:The 2nd optical barrel 7 of a subordinate lens system is provided with a filter 9 for adjusting the quantity of transmitted light, and when the subordinate lens system and the main lens system of the 1st optical lens barrel 1 are combined together to switch focal length, the quantity of light photodetected by a photometric photodetecting element 11 decreases. Therefore, the quantity of photodetected light which corresponds to an angle of photographic photodetection with the same aperture value and same ratio is detected by the element 11 without interlocking adjustment before and after the focus switching, and exposure compensation which accompanies variation in F number is performed by the simple constitution. |
