The small dimensions of the focal planes of solid-state sensors and the limited resolution of the pixel array decrease the potential applications of vision systems. Zoom lenses can enhance the flexibility and capabilities of vision systems by providing the user with continuous access to a full range of focal length settings without degrading geometric accuracy. The key to the use of such lenses lies in the inherent stability of array cameras. Preliminary test results showed that when the focal length setting of a zoom lens was changed, significant changes occurred in both the position of the principal point and lens distortion characteristics. However, these changes were found to be either linear or curvilinear over the entire range of zoom. Moreover, both the magnitude and pattern of the changes were found to be highly stable over a period of weeks. Thus, the results indicated that the changing interior geometry of zoom lens camera systems can be pre-calibrated and then applied during the measurement process. This paper reports on experimental results and distortion models using two zoom lenses with focal lengths ranging from 12.5mm to 75mm.