Cooke S4 optics offer superb optical and mechanical performance, control of flare, distortion, veiling glare and spherical aberrations at full aperture. The cam-type focus mechanism allows for smooth focus adjustments. All of our S4 Prime lenses are now equipped with /i Technology, as of February 2005. S4/i lenses are designed for all PL mounted professional motion picture film and electronic cameras. The /i Technology provides cinematographers and camera operators with vital information on lens setting, focusing distance, aperture and depth-of-field, hyperfocal distance, serial number, owner data, lens type and focal length in both metric and footage measurements. For zoom lenses, the zoom position is displayed.