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TECHNOLOGY FEATURE VIDEO GUIDE


what would usually be regarded as the main action, everything is in sharp focus. The main criteria for selecting a lens are: resolution, contrast, colour rendition, and breathing. Resolution comes down to the smallest particle of light in an image that can be captured accurately. The contrast of a lens is determined by whether it has a short/hard or a long/gentle tonal range (tones are the shade or tint of a colour in an image). Colour rendition helps give each make of lens individual characteristics, such as a cold or warm look. It is based on two parameters: the total colour hue of what is being photographed and fringing: the effect of either one or many coloured lines appearing round the edge of a picture. This is caused when the lens cannot focus all the colours in the visible spectrum on precisely the same spot. Breathing occurs when the size of an image changes as the lens focus is altered, something that, according to cinematographer and author Paul Wheeler, is most common with video camcorder lenses.


LOOKING FORWARD New lenses have been produced over the years but the basics of the craft remained the same until the last 10 years. The coming of high-definition acquisition, production, and projection/transmission caused cinematographers, camera operators, and lens manufacturers to re-evaluate


standard-definition lenses and ask whether they were up to working with new HD media. Those in film argued that the high resolutions of the format meant they had been working in HD for years anyway and there was no need to change their lenses. The situation was different in TV. SD lenses were found wanting in terms of resolution, so the main manufacturers produced a new generation of glass for HD. While SD lenses are considered unsuitable for HD, new high-def models can be used for standard def; the only consideration is that the circle of confusion – the biggest dot on the recorded image that still appears sharp under the most exacting viewing conditions and which is used to calculate depth of field charts – is larger. A similar discussion is now being had over the emergence of 4K cameras and distribution. Some manufacturers, including Fujifilm are beginning to produce specific 4K lenses but others in the business see this as unnecessary. Guy Genin at Cooke Optics outlines that over the last 30 years lenses have been designed to be faster, with improved contrast and better control of aberrations. The main change lenses have had to deal with, he says, has been frame size; moving from the almost square Academy format (22mm horizontal by 16mm vertical with a 27.2mm diagonal) to 24mm by 18mm (30mm diagonal), calling for the lens to resolve over 200


PRODUCTFOCUS


Fujifilm ZK4.7x19 PL 19-90 Cabrio Lightweight zoom www.fujifilm.eu


Key Features: • Focal length: 19-90mm • Zoom rotation: 4.7× • Maximum photometric aperture T-No: 1:2.9


• Iris blades: 9 • M.O.D. (Mean Optical Density, from image plane): 0.85m


• Object dimensions at M.O.D: 19mm 915 × 515mm 90mm 193 × 109mm


• Angular field of view: 16:9, 19mm 71°41' × 44°14' 90 mm 17°20' × 9°48'


• Macro: Available • Filter thread: M114 • Size (diameter by length): 114 × 223mm • Mass (without lens hood): 2.7kg


The PL 19-90 Cabrio (ZK4.7x19) is part of the recently introduced ZK Series of high-definition PL-mount 35mm zoom lenses. It offers a detachable servo drive unit, which means it can be used as both a standard PL lens and an ENG-style optical. Among other features of the ZK4.7x19 are flange focal distance adjustment and macro function, with LDS (Lens Data System) and /i metadata compatibility. Fujifilm claims that the lens has the longest possible focal range for a lightweight model.


line pairs a millimetre in the image field. Genin argues that with all the processing and filtering involved in 4K capture the real limitation on the image produced is the camera itself, not the lens.


REFERENCES The Complete Film Dictionary second edition by Ira Kongigsberg, Penguin Reference 1997 High Definition and 24p Cinematography by Paul Wheeler, Focal Press 2003 Are your lenses good enough for that 4k high definition camera? by Guy Genin, Cooke Optics www.cookeoptics.co.uk


“The main criteria for selecting a lens are: resolution, contrast, colour rendition, and breathing.” Kevin Hilton


TECHNOLOGYNEWS


During this month’s IBC in Amsterdam Cooke Optics will be showing its miniS4/i, S4/i, 5/i and anamoprhic/i lenses, along with the first production model from the recently announced range of Metrology lens testers. So far this year Cooke has introduced new anamorphic lenses,


www.audiomedia.com


developed with Thales Angenieux, and its Metrology lens-testing product. It has also received an Academy Award and Cine Gear Expo Award. The Oscar was bestowed for the company’s “continuing innovation in the design, development and


manufacture of advanced


camera lenses that have helped define the look of motion pictures over the last century”. The Cine Gear Expo 2013 Technical Lifetime Achievement Award recognised "the significant contributions Cooke has made advancing the art and craft of filmmaking”.


Cooke Optics’ Les Zellan with the company’s Oscar


September 2013 57


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