Large aperture retrofocus lens

A large aperture retrofocus lens system comprising a first lens L.sub.1 which is a positive meniscus lens convex toward the object side, a second lens L.sub.2 which is a negative meniscus lens convex toward the object side, a third lens L.sub.3 which is a negative meniscus lens convex toward the image plane, a fourth lens L.sub.4 which is a negative meniscus lens convex toward the object side, a fifth lens L.sub.5 which is a positive refracting power double-convex lens having the face of greater curvature faced to the object side and a sixth lens L.sub.6 which is a positive meniscus lens convex toward the object side, the first to sixth lenses being arranged in this order from the object side;

• wherein the lens system satisfies the following formulae,
• -5.0f.ltoreq.r.sub.5 .ltoreq.-0.3f (1)
• -0.75.ltoreq.f/f.sub.3 .ltoreq.0.5 (2)
• 30>.nu..sub.4 ( 3)
• 42<(.nu..sub.5 +.nu..sub.6)/2 (4)
• 1.65<(n.sub.5 +n.sub.6)/2 (5)
• where n.sub.i represents the refractive index of the i-th lens, r.sub.5 represents the radius of curvature of the object side surface of the third lens (r.sub.5 <0), f.sub.3 represents the focal length of the third lens, f represents the focal length of the overall lens system, and .nu..sub.i, represents the Abbe's number of the i-th lens.

A large aperture retrofocus lens system comprising a first lens L.sub.1 which is a positive meniscus lens convex toward the object side, a second lens L.sub.2 which is a negative meniscus lens convex toward the object side, a third lens L.sub.3 which is a positive meniscus lens convex toward the image plane, a fourth lens L.sub.4 which is a double-concave lens of negative refracting power having the face of greater curvature faced to the image plane side, a fifth lens L.sub.5 which is a double-convex lens of positive refracting power having the face of greater curvature faced to the object side and a sixth lens L.sub.6 which is a positive meniscus lens convex toward the object side, the first to sixth lenses being arranged in this order from the object side;

• wherein the lens system satisfies the following formulae,
• -5.0f.ltoreq.r.sub.5 .ltoreq.-0.3f (1)
• -0.75.ltoreq.f/f.sub.3 .ltoreq.0.5 (2)
• 30>.nu..sub.4 ( 3)
• 42<(.nu..sub.5 +.nu..sub.6)/2 (4)
• 1.65<(n.sub.5 +n.sub.6)/2 (5)
• where n.sub.i represents the refractive index of the i-th lens, r.sub.5 represents the radius of curvature of the object side surface of the third lens (r.sub.5 <0), f.sub.3 represents the focal length of the third lens, f represents the focal length of the overall lens system, and .nu..sub.i represents the Abbe's number of the i-th lens.