Zoom lens system and imaging apparatus having the same

A zoom lens system comprising:

• a plurality of lens units, including:
• a first lens unit with positive optical power;
• a second lens unit with negative optical power;
• a third lens unit with positive optical power;
• a fourth lens unit with positive optical power;
• a fifth lens unit with negative optical power;
• and
• a sixth lens unit with positive optical power,
• wherein the first through sixth lens units are disposed from the object side to the image side along the optical axis, respectively,
• wherein spaces are provided between adjacent lens units,
• wherein during a zooming operation, the spaces change, wherein the fifth lens unit is movable so as to have a direction perpendicular to the optical axis, and
• wherein a focal distance fis of the fifth lens unit and a focal distance ft of the zoom lens system at a telephoto end satisfy the following condition:
• 0.05<|fis|/ft<0.25, wherein a composite focal distance fRB1t of the third lens unit and the fourth lens unit at the telephoto end satisfies the following condition:
• 0.05<fRB1t/ft<0.2.