Patent ID: 8223436

Claim:
A rear attachment lens detachably attached to a main lens system at an image side of the main lens system to lengthen a focal length from a focal length of the main lens system itself, the rear attachment lens comprising: a negative lens disposed such that, when L is a distance between a lens surface closest to an object side and a lens surface closest to an image side in the rear attachment lens, the negative lens is within an area in which a distance from the lens surface closest to the object side in the rear attachment lens is in the range of 0.5 L to 1.0 L, wherein, when νdn1 is an Abbe number of a material of the negative lens with respect to the d-line and θgFn1 is a partial dispersion ratio of the material of the negative lens with respect to the g-line and the F-line, the following conditions are satisfied: 10<νdn1<23 0.020 <θgFn 1−0.6438+0.001682 *νdn 1<0.100.