a zoom lens consisting of a front lens portion having a plurality of lens units which are separated from each other by spaces which vary for zooming , and a rear lens portion comprising an image forming relay lens group for introducing rays of light emitted from the front lens portion to an image surface . the rear lens portion consists of a front relay group that is widely spaced ahead of a rear relay group . the rear relay group comprises a first movable lens group having a positive refractive power that moves along the optical axis for macro photography , and a second movable lens group having a positive refractive power that independently moves along the optical axis to adjust tracking .