In a lens system, a first lens having negative optical power and a meniscus shape with a convex surface facing an object side, a second lens having positive optical power and a double-convex shape, a third lens having negative optical power and a double-concave shape, a fourth lens having positive optical power, and a fifth lens having positive optical power and a double-convex shape are arranged sequentially from a front side to a rear side. Letting D1,2 be an interval between said first and second lenses, D2,3 an interval between said second and third lenses, bf be a back focus of the entire system, and f be a focal length of the entire system, at least one of three conditions given by 0.61,2/f<1.0, 0.552,3/f<0.85, and 0.9

 
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