Retro focus type wide-angle lens apparatus using the same

A retro focus type wide-angle lens comprising, successively from an object side, a front group having a negative refracting power and a rear group having a positive refracting power;

• said front group comprising, successively from the object side, a first lens made of a negative meniscus lens having a convex surface directed onto the object side, a second lens made of a biconvex lens, a third lens made of a negative meniscus lens having a convex surface directed onto the object side, and a fourth lens made of a positive meniscus lens having a concave surface directed onto the object side;
• said rear group comprising, successively from the object side, a cemented lens in which a fifth lens made of a negative lens and a sixth lens made of a positive lens are cemented together, and a seventh lens made of a positive lens having a convex surface directed onto the object side;
• said retro focus type wide-angle lens satisfying the following conditional expressions (1) and (2):
• 0.6<ƒ′/I<0.85 (1)
• 0.45<|ƒ′G1/DG1-2|<0.88 (2)
• where
• f′ is the focal length of the whole system;
• I is the diagonal length of an effective screen;
• f′G1 is the focal length of the system formed by the first to third lenses;
• and
• DG1-2 is the distance from the object-side surface of the first lens to the imaging-side surface of the fourth lens.