Leading British manufacturer of optical products and zoom lenses is Rank Optics-Taylor Hobson who carry on the tradition of Taylor, Taylor & Hobson of Leicester, England who made the 'Cooke' lens on which the film industry grew up. This tradition of optical manufacture owes much to William Taylor who also did pioneering work on standards and gauging. The present day zoom lens is a complex combination of optics, mechanisms and electronics which requires a unique combination of traditional skills and modern technology to meet the demands made on it. The mechanical components have to be made to close tolerances and a tradition of machine adaptation has enabled very high standards of finish to be achieved under production conditions. Air-bearing spindles combined with special diamond cutters produce finishes better than 0.025 micrometres Ra. Thread chasing comprises a considerable proportion of turning and machines with automatic chasing attachments produce threads in ferrous and non-ferrous materials at high outputs. And the employment of numerically controlled milling machines substantially reduces tooling costs. Nevertheless, the skill and experience of the craftsmen still play an essential part in lens production.