| 摘要 |
A photographic lens system which is composed, in order from the object side, of a first lens element having a positive refractive power, a second lens element having a negative refractive power, a third lens element having a positive refractive power, and a fourth lens element which has an aspherical surface on the image side and a negative refractive powers. An aperture stop is disposed between the second lens element and the third lens element or between the third lens element and the fourth lens element. This photographic lens system has a large aperture, favorable optical performance within a photographing range from infinite distance to an extremely short distance, a compact size and a simple composition, and can be manufactured at a low cost.
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