PURPOSE: To satisfactorily correct aberrations and to shorten the overall length of a lens system to make it miniaturized and light-weight by satisfying a specific condition between radiuses of curvature of the object-side surface and the image- side surface of a first lens group consisting of a positive meniscus lens whose convex is directed to the object side.

CONSTITUTION: In the case of the use for reduction power, a first lens group I consisting of a positive meniscus lens whose convex is directed to the object side, a second negative lens group II, a third positive lens group III, and a fourth lens group IV consisting of a positive meniscus lens whose convex is directed to the object side are provided in order from the object side. This lens system satisfies condition 0.17<r1/r2<0.40 where r1 is the radius of curvature of the object-side surface of the first lens group I and r2 is that of the image-side surface of this group I. Thus, the miniaturized and light-weight lens system where aberrations are satisfactorily corrected is obtained.