| 摘要 |
PURPOSE:To satisfactorily correct the shifting of aberrations, especially, the spherical aberration and the astigmatism in case of focusing by moving third-fifth lens groups which are partial lens groups satisfying a prescribed condition of the rear group of a telephoto lens to focus the lens. CONSTITUTION:This telephoto lens system is provided with a first lens group I which has plural lenses and has a positive refracting power as the whole, a second lens group II having a negative refracting power, the third lens group III which has a lens having a positive refracting power and a lens having a negative refracting power stuck to each other and has a negative refracting power as the whole, the fourth lens group IV having a negative refracting power, and the fifth lens group V having a positive refracting power which are arranged in order from the object side. This lens system satisfies the condition of an inequality I where (f) is the focal length of the whole of the lens system and L is the interval between first and second lens groups I and II. The third lens group III, the fourth lens group IV, and the fifth lens group V are moved together to the image surface side and the fourth lens group IV is moved more quickly than the third lens group III and the fifth lens group V to focus the lens system from an object at the infinity to an object at a close distance. Thus, the variance of aberrations, especially, in case of focusing is satisfactorily corrected.
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