| 摘要 |
PURPOSE:To obtain a Gauss type photographic lens which a moving extent of a focusing lens is small and an aberration is corrected satisfactorily, by satisfying prescribed conditions, in a lens system constituted of five groups of a positive lens, a negative lens, a cemented lens of positive and negative lenses, a positive lens and a negative lens in order from an object side. CONSTITUTION:In a lens system consisting of five groups of a positive lens, a negative lens, a cemented lens of positive and negative lenses, a positive lens and a negative lens in order from an object side, the focusing is executed by moving the third group and the fourth group as one body on the optical axis, and also the conditions of the following expressions are satisfied. 0.6<f3,4<0.9, 2<¦f5/F¦<8, f5<0 (provided that, f3,4, f5 and F denote a composite focal distance of the third group and the fourth group, a focal distance of the fifth group and a focal distance of the whole system, respectively). By the first conditional expression, a moving extent of a focusing lens is suppressed small and also the aberration is corrected easily. By the second conditional expression, the aberration is corrected easily. In this way, it is possible to obtain a Gauss type photographic lens by which a moving extent of a focusing lens is small and an aberration is corrected satisfactorily. |
