Television lenses

By Lyudmila Berezentseva

Review contents:
Television lenses of the third millennium beginning Television lenses Lenses from “Optics-Elite” Lenses from Angenieux New lenses from Canon E-cinema lenses from Fujinon Fujinon lenses for TV journalism and TV production

The foreign camcorders purchased by domestic TV companies, are completed by different lenses. At present world producers of TV optics such as Angenieux, Canon and Fujinon offer the more than 120 products. All of these differ on technical features and purposes.

The television lenses either for standard definition television (SDTV), or for HD television, it is possible to divide into the main groups according to the application type as following:

• For field shooting;
• For studio transmissions;
• For Electronic News Gathering (ENG) and field TV production;
• For professional shooting;
• For E-cinema;
• For teleconference, macroshooting etc.

The lenses for field TV production

The lenses of this class have a big range of the focal length change (from 80× to 101×), high value of relative aperture (from 1:1.4 to 1:1.6), as well as reliable protection from dust, humidity and the temperature drops (they contain the compartment for condensate removing).

At present the XA101×8.9 BESM (Fujinon) and HJ100×9.3 BIE (Canon) lenses are records on multiplicity. With double multiplexer they have the maximum focal length equal to 1800 and 1860 mm accordingly.

The development of lens with extremely long focal length (from 72× to 101×) became possible due to creation of the following technologies: Optical Stabilized Technology (OS-Tech) — Fujinon, or of Optical Shift Image Stabilizer (Shift-IS) — Canon).

Stabilization unit from Fujinon is set between camera and lens, as well as can be built-in (HA87×). The unit has the system of the offset of the optical scene with sensors of the vibration, which compensate the offset of beams, appearing at vibrations of the picture. When use the built-in adapter OS-Tech the focal length of the lens does not change. The external adapter is easy fixed between lens and camera (its length is about 48 mm), and focal length of the lens increases in 1.25 times. Antivibrator function is switched on by simple control button pressure. Herewith the stabilization unit can be used with many lenses produced by this company (Ah60×, XA76× and others).

The Canon stabilizer presents itself a group of the lenses (IS), which moves in a plane, parallel to picture plane. This unit is switched on in the moment, when signal sensors, checking rotation angle value and vertical/horizontal offset, will send information in 32-bit microcomputer. New optical stabilization technology provides the broadcasting quality even under maximum focal lengths in condition of the 10-Hz vibration.

Lenses for studio/field application

To the main technical requirements for studio lenses, it is possible to refer the following: angle of the field of vision can not be less than 60°; minimum distance to shooting object can not be more than 0.6 m; relative aperture is 1:1.5; multiplicity can not be not less than 20×. As a rule, their weight must be in the range from 15 to 20 kg. All modern lenses are corresponded to these requirements, since due to high quality and introduction of digital technology, their possibilities are vastly extended.

The main trends in creation of new and modernization of the early developments are became the application of a system of automatic digital control in modern studio/field lenses. This system some years ago was realized only in several lens models, mainly for HDTV, but today practically all lenses of the different destination provided by digital control. This system vastly enlarges the reliability and accuracy of the optics functionality as well satisfies to all requirements of the broadcasting systems of the last generation. Digital autocontrol is realized in all lenses of Digital (Angenieux), Digi Super (Canon) and Digi Power (Fujinon) series.

The general features of each of them are the following:

• Compensation of the scaling effect at focusing on a distance (the storing of the vision field angle — Anti-Breathing Device (Angenieux), CAFS (Canon), Zooming Effect (Fujinon);
• Presence of microcomputer in each automatic controller, which with 13-bit accuracy controls by scaling and focusing and with 10-bit accuracy controls by diaphragm;
• Possibility of the remote control by scaling, focusing and diaphragm;
• Presetting of one frame with storage of zoom/focus position;
• Choice of different velocities and types of the scaling;
• Check of the luminosity constancy at reduction of the relative aperture at high focal lengths;
• Internal focusing;
• Possibility of the switching the frame format 16:9/4:3 (ratio converter — Fujinon, crossover — Canon, with increase 0.8× for conservation of the vision field angle);
• Possibility of the quick focus and scaling settings;
• Mechanism of a fluent back focus tuning (Zoom Track — Canon, AB focus — Fujinon);
• Full compatibility with analog accessories.

Nevertheless there are some differences. For operative control of Fujinon lens features the system of the diagnostics Find System is used, which checks an actual values of diaphragm, scaling and focusing parameters and compares them with nominal values. The results of the diagnostics are displayed in digital code on panel of the lens casing. The Angenieux company the digital display control ADS (Advanced Display System) is used. This system provides quick and exact control of functional units, allows to tune and to correct (through portable display) all installed working parameters: the diaphragm value, depth of the field, focal length, distance of the shooting, position of the multiplexer, scaling versions, as well to enter new values, depending on shooting conditions change. There is digital unit for storing of six positions of zoom and focus.

Lenses for ENG-cameras and cameras for field TV-production

The lens nomenclature of this class is enough wide. Its particularity is a realization of the high technical features under the least size and weight.

Some of the models are released for several years, and many operators could value their high quality, simplicity and suitable application. The most lens of different companies have approximately the same technical features, and operators can easy choose the lens type required for different conditions of the shooting. Many lenses are a last development of 2001…2003 years. Particularities of this class lens is a presence of aspheric glasses, a special covering for contrast increasing, an internal focusing, a compatibility with 16:9 format, a double engraving of focusing range (in meters and foots), semiautomatic and completely autocontrol by scaling and focusing.

Lenses for professional applications

It is necessary to notice that lens of this class, in contrast with lenses of broadcasting quality, under the same values of resolution the MTF value is decreased from 20 to 30%. They it is enough popular, have an optimum ratio of the price and quality, provided by simple control, compactness and light design.

The main trend of this class lenses development is an approach to broadcasting quality by means of their optical features improvement (entering of the internal focusing, allowing lowering the distortion and to minimize the chromatic aberrations, entering of macroshooting mechanism and double multiplexer). So in YJ19× lens from Canon is the function Shuttle Shot is entered, which allows raising the scaling rate to 1.7 s. The wide-angle A13×4.5 BERM, HA13×4.5 BERM, A13×6.3/S13×4.6 BERM lenses from Fujinon provided by all advantages of Wide Power technology, allowing to reach the greater multiplicity (13×) under wide vision field angle (accordingly 94° and 70°). The standard A20×8.6/S20×6.4 BERM lens has a high quality optics, the reliable and strong design, suiting for daily application.

Lenses for E-cinema

The lenses of this series are become popular at the last years. They allow to get the clear picture (practically without distortion), with quality comparable with frames, shot on 35mm film. These products have a ratio of the modulation transmission to more than 92% in the centre of the frame and more than 84% on field of the frame.

All lenses of this class have a high optical quality, minimum distance of the shooting, constant relative aperture on all range of the focal length changes, internal focusing without zoom of the picture, mechanism of the exact back focus tuning. They have a clear engraving of values of the scaling, distances and diaphragms. The indication of the scales is big and very suitable for reading; counting out of distances is valued from picture plane, as in lenses for film cinema. The lenses are provided by adjusting rings of the focus, scaling and diaphragm with gear module equal to 0.8. They are compatible with existing remote control systems, by means of lengthened handles there is possibility of manual control of diaphragm, scaling and focusing. The system of digital control provides very high accuracy of the installation of all lens parameters.

The new lenses for E-cinema are the result of the joint work with camcorder producers, TV and cinema operators.

In conclusion it is possible to note the main trends of the optics development for digital TV camcorders:

• Quality improvement of optical systems;
• Introduction of digital control of functional lens units that has vastly raised accuracy and reliability of the functioning;
• Introduction of picture stabilization both for field lens, and for ENG lens;
• Presence of the format switch for all camera types;
• Operative and efficient control of all lens features;
• Increase of the range multiplicity of the focal lengths at reduction of the weight and size both for lens of field application, and for ENG-cameras;
• Ergonomics improvement of drive for comfort exploitation.