Patent ID: 7675693

Claim:
An optical accessory arranged to change an optical characteristic of a shooting lens and to be detachably attached to an object side of a shooting lens, the optical accessory comprising: at least one lens FE having a negative refractive power, an image-side surface of the lens FE being an aspherical surface having a negative refractive power that decreases from the optical axis to its peripheral portion; wherein the following conditions are satisfied: 8.0×10 −4 <|Δ7 /fe|< 2.0×10 −2 , 0.3<|Δ4/Δ7|<0.65, and 0.4<|Δ9/Δ7|<1.0, where fe represents the focal length of the lens FE, and Δ 9 , Δ 7 and Δ4 respectively represent the aspherical amounts at the image heights of 90%, 70% and 40% of the effective diameter of the lens FE having the aspherical surface, the aspherical amount is defined by a distance between the aspherical surface of the aspherical lens FE and a spherical surface along the optical axis direction, where the spherical surface has a center of curvature radius on the optical axis and contains three points: a vertex of the aspherical lens FE; and both ends of the maximum effective diameter of the aspherical lens FE.