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
