The design and manufacture of zoom lenses involves a range of scientific and engineering problems not normally encountered in fixed focal length lens manufacture. This is not solely related to the increased number of elements but also to the manner of use of such lenses. Two lenses are described to illustrate different approaches to the problems. In one lens having a specification of 25-250mm f/3.6 for 35mm cine the zoom action is achieved by sliding movements. In the second lens the specification is 20-100mm f/2.8 and the zoom action is obtained by rolling movements. The latter lens also achieves a shorter minimum object distance and superior optical performance. The lens elements are located in steel cells which are cemented into aluminium carriages using a flexible adhesive so as to obtain improved alignment over a wide temperature range.