| 摘要 |
A macro lens system has, from the object side, a first lens group; a second, positive, lens group; and a third, negative, lens group. Focusing from an object at infinity to an object at a close distance is achieved by moving only the second lens group toward the object side along the optical axis while keeping the first and third lens groups stationary, and the conditional formulae ² ‰¤ -0.45 (² representing the lateral magnification with focus on the closest object) and 0.4 < f2 / f < 0.68 (f2 representing the focal length of the second lens group, f representing the focal length of the macro lens system as a whole with focus on an object at infinity) are fulfilled. |
