Field of the Invention
The present invention relates to a zoom lens and an imaging apparatus.  In particular, the present invention relates to a zoom lens used in an electronic camera, such as a digital camera, a camera for broadcasting, a camera for surveillance and a camera for film making, and also to an imaging apparatus including the zoom lens. 
Description of the Related Art
In zoom lenses used in imaging apparatuses, such as a video camera and an electronic still camera using imaging devices, such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor), as recording media, a request for higher variable magnification ratios is increasing.  As a type of zoom lens achieving a high variable magnification ratio, a five-group-type zoom lens in which a positive group, a negative group, a positive group, a negative group and a positive group are arranged in this order from the object side is known (for example, Japanese Unexamined Patent Publication No.  2007-047538 (Patent Document 1), Japanese Unexamined Patent Publication No.  2008-304706 (Patent Document 2), Japanese Unexamined Patent Publication No.  2009-282429 (Patent Document 3), and Japanese Unexamined Patent Publication No.  2011-186417 (Patent Document 4)).