Imaging optical system having specified relationship between focal length, abbe number, and partial dispersion ratio, and imaging apparatus having the same

An imaging optical system comprising, in order from an object side to an image side,

• a first lens unit which has a positive refractive power,
• a second lens unit which has a negative refractive power and moves in an optical axis direction in focusing,
• a third lens unit which has a positive or a negative refractive power, and
• an aperture stop arranged in a position closer to the image side than the first lens unit,
• wherein the third lens unit includes one or more partial lens units which are immovable during focusing and during image blur correction, each having a positive or a negative refractive power,
• wherein each of the one or more partial lens units includes one or more positive lenses, and
• wherein the following conditional expressions are satisfied:
• −2.5<f1/f2<−1,
• 3.0<f2/(f1×L)<8.0, and
• -
• 0.0150
• <
• ∑
• i
• =
• 1
• n
• ⁢
• ⁢
• Δ
• ⁢
• ⁢
• θ
• gFPi
• ×
• f
• f
• Pi
• ×
• v
• dPi
• <
• -
• 0.0040
• ,
• where a focal length of the first lens unit is f1, a focal length of the second lens unit is f2, an overall lens length is L, a focal length of the imaging optical system when focused on an infinite-distance object is f, a focal length of an i-th positive lens in an i-th position, among all of the one or more positive lenses, counted in order from the object side to the image side is fPi, an Abbe number and an anomalous partial dispersion ratio difference of a material for the i-th positive lens are νdPi and ΔθgFPi, respectively, and a total number of the one or more positive lenses included in the one or more partial lens units is n.