The KH21ex5.7 mobilized the best in portable EFP optical design criteria to achieve a remarkable lens offering focal lengths up to 120mm (or 240mm with extender) and a wide-angle of almost 63 degrees horizontal. Combined with an exceptionally high sensitivity (F1.4 maximum aperture) this is a lens that can encompass an unusually broad range of shooting situations.
The KH21ex5.7 utilized breakthrough technologies and powerful computer-aided design techniques to produce a very wide-angle HDTV lens with an excellent performance-cost optimization. It is a design directly responding to the expressed creative desires of broadcasters and HD producers for low-cost HD acquisition system.
The KH21ex5.7 represents a fine compromise between the demands for mobility in a handheld HDTV camera system and the high imaging performance requirements for HDTV production. The requisite optimization strategies to achieve this balance sought a high MTF over the entire image plane, minimization of chromatic aberrations, and maximization of image contrast. Relative light distribution was optimized for the more open aperture settings and this uniformity of brightness across the image plane combines with the high contrast and excellent picture sharpness to produce vividly clear HD pictures. Contrast was extended by careful control of black reproduction – with optical and mechanical design innovations that substantially reduced flare, veiling glare, and any internal reflections. Tight control of the geometric distortion at wide-angle settings constituted another central design imperative. The lens spectral transmittance characteristic was closely coordinated with that of all of the major portable cameras to ensure adherence to the HDTV colorimetric standards and to additionally support flexible creative control of color reproduction.
- Optical Technologies – Optical materials combined with the very latest lens element design innovations and multilayer coatings – that produce an unsurpassed pristine imaging system for the most discerning production team
- Internal Focus – A Canon design innovation that uses a floating optical system to better control chromatic aberrations
- Digital Technologies – Third-generation enhanced digital servo systems using Canon-developed 16-bit optical rotary encoder devices introduce entirely new value-added creativity to handheld acquisition systems
- 16-bit rotary encoder for aperture control reports to the associated camera Iris control system (10-bit compatibility)
- Maximum Zoom speed is 0.5 seconds and Focus is 1.5 seconds
- Mechanical Technologies – Ergonomic mechanical design that produced this HD lens having the same size and weight as its SDTV predecessor
- Compact digital servo drive unit is mounted to the lens at a 12.5 degree angle for comfort and balance
- Magnesium alloy body for light weight and exceptional durability
- Ecological Design – All contemporary Canon lenses avoid the use of materials and substances potentially harmful to the environment