Cooke S4/i Prime Lenses were designed and developed in close technical collaboration with industry professionals. Cooke S4/i 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. Modular construction increases ease of maintenance and serviceability.All of our S4 Prime lenses (and CXX zoom lens) are now supplied 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.