Zoom lens system, imaging device and camera

A zoom lens system, in order from an object side to an image side, comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein

• in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit, the second lens unit, the third lens unit and the fourth lens unit are moved individually along an optical axis such that air spaces between the individual lens units should vary, so that variable magnification is achieved, wherein
• at least one of the lens elements constituting the second lens unit satisfies the following condition (I-2), and wherein
• the following conditions (a) and (b) are satisfied:
• 11.8<fW/tLG2<500.0 (1-2)
• ωW≧30 (a)
• fT/fW4.5 (b)
• where,
• tLG2 is a center thickness of the lens elements constituting the second lens unit,
• ωW is a half view angle (°) at a wide-angle limit,
• fT is a focal length of the entire system at a telephoto limit, and
• fW is a focal length of the entire system at a wide-angle limit.

A zoom lens system, in order from an object side to an image side, comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein

• the third lens unit includes at least one set of cemented lens element, wherein
• in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit, the second lens unit, the third lens unit and the fourth lens unit are moved individually along an optical axis such that air spaces between the individual lens units should vary, so that variable magnification is achieved, and wherein
• the following conditions (1-3), (8), (a) and (b) are satisfied:
• 53<(fT/fW)×fG1/tG1<900 (1-3)
• 0.15<tG3ce/tG3<0.39 (8)
• ωW≧30 (a)
• fT/fW≧4.5 (b)
• where,
• fG1 is a composite focal length of the first lens unit,
• tG1 is a thickness of the first lens unit, wherein an optical axial distance measured from the object side surface of the most object side lens element to the image side surface of the most image side lens element,
• tG3ce is a center thickness of the cemented lens element of the third lens unit,
• tG3 is a thickness of the third lens unit, wherein an optical axial distance measured from the object side surface of the most object side lens element to the image side surface of the most image side lens element,
• ωW is a half view angle (°) at a wide-angle limit,
• fT is a focal length of the entire system at a telephoto limit, and
• fW is a focal length of the entire system at a wide-angle limit.

A zoom lens system, in order from an object side to an image side, comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein

• in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit, the second lens unit, the third lens unit and the fourth lens unit are moved individually along an optical axis such that air spaces between the individual lens units should vary, so that variable magnification is achieved, and wherein
• the following conditions (1-4), (6), (a) and (b) are satisfied:
• 83<(fT/fW)×fG4/tG4<900 (1-4)
• 4.0<fG4/fW<8.0 (6)
• ωW≧30 (a)
• fT/fW≧4.5 (b)
• where,
• fG4 is a composite focal length of the fourth lens unit,
• tG4 is a thickness of the fourth lens unit, wherein an optical axial distance measured from the object side surface of the most object side lens element to the image side surface of the most image side lens element,
• ωW is a half view angle (°) at a wide-angle limit,
• fT is a focal length of the entire system at a telephoto limit, and
• fW is a focal length of the entire system at a wide-angle limit.