| 摘要 |
PURPOSE:To perform high-performance floating while compensating excellently aberrational variation when a body in a wide long and short distance range is put in focus by composing a photographic lens of four groups and moving them specific conditions. CONSTITUTION:This photographic lens has a 1st group I with positive refracting power, a 2nd lens group II with positive refracting power, a 3rd lens group III with negative refracting power, and a 4th lens group IV with positive refract ing power i.e. four lens group in order from an object side. When focusing is performed from an infinite distance body to a short-distance body, the floating is carried out by moving the 1st-4th lens groups I-IV so that three all of air formed of two adjacent lens group respectively increased. Then when the short-distance object is put in focus, only the 4th lens group IV is moved on the optical axis to vary optical characteristics. Consequently, some lens groups which have aberrations compensated excellent and utilized the floating are used to reduce a stopping-down quantity, specially, at the time of short-distance photography and vary image plane characteristics mainly and optionally.
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