Zoom lens and imaging apparatus

A zoom lens including a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power, a fourth lens group having negative refracting power and a fifth lens group having negative refracting power in order from an object side;

• wherein a surface of the fifth lens group disposed closest to the object side is concave;
• wherein the lens groups move in magnification change from a wide angle end to a telephoto end such that a gap between the first lens group and the second lens group increases and a gap between the second lens group and the third lens group decreases;
• a negative lens group disposed closer to an image plane side than a diaphragm among all lens groups is set as a focusing lens group, and the focusing lens group moves toward the image plane side in focusing from infinity to a close object;
• the zoom lens satisfies conditional expression (1);
• and the focus lens group is composed of a single lens block of a meniscus shape having a concave surface at image plane side, and satisfies conditional expression (2) below:
• [Expression 1]
• 0.45≦β5T/β4T≦1.900 (1)
• where
• β4T:
• Lateral magnification in telephoto end of fourth lens group
• β5T:
• Lateral magnification in telephoto end of fifth lens group
• [Expression 2]
• 3.10≦ra4/rb4≦210.00 (2)
• where
• ra4:
• Curvature radius of object side surface of focus lens group
• rb4:
• Curvature radius of image plane side surface of focus lens group.