Patent ID: 8462440

Claim:
An optical system comprising a lens unit GLN including at least one lens unit having a negative refractive power which is disposed closer to an object side than an aperture portion SP, wherein, when a relative partial dispersion difference and an Abbe number of a material of a negative lens included in the lens unit GLN are denoted by ΔθLN and νLN, respectively, a negative lens satisfying the following conditions: 0.006 <ΔθLN and 60 <νLN is denoted by a negative lens LNlow, the number of the negative lenses LNlow is denoted by SUM(LNlow), a negative lens satisfying the following conditions: 0.006 <ΔθLN and νLN< 25 is denoted by a negative lens LNhigh, the number of the negative lenses LNhigh is denoted by SUM(LNhigh), the number of lenses included in the lens unit GLN is denoted by SUM(L), the number of negative lenses included in the lens unit GLN is denoted by SUM(LN), a sum of relative partial dispersion differences of materials of the negative lenses included in the lens unit GLN is denoted by SUM(ΔθLN), a negative lens having a minimum Abbe number among the negative lenses included in the lens unit GLN is denoted by a negative lens LNmin, an Abbe number thereof is denoted by νLNmin, a negative lens having a maximum Abbe number among the negative lenses included in the lens unit GLN is denoted by a negative lens LNmax, an Abbe number thereof is denoted by νLNmax, a distance between an object-side surface vertex of the negative lens LNhigh and the aperture portion SP is denoted by dNS, and a distance between the most-object-side lens surface vertex and the aperture portion SP is denoted by d1S, the following conditions are satisfied: 0.60<SUM( LN )/SUM( L )<1.00, 0.70<(SUM( LN low)+SUM( LN high))/SUM( LN ), 3.50 <νLN max/ν LN min<6.50, 0.30 <dNS/d 1 S≦ 1.00, and 0.065<SUM( ΔθLN )<0.250, and wherein, when the optical system is a zoom lens, the position of the aperture portion SP is a position defined when the zoom lens is at a wide-angle end.