Third Generation Flagship Studio Lens, Available with Auto Focus
The worldwide explosion in HDTV production and the emerging interest in 1080/60P/50P studio origination spurred the desire for increasingly higher performing HD studio lenses. The design of this third-generation HD studio lens sought the highest possible image performance in the 2/3-inch image format. A decade of progressive advances in optical design techniques, optical materials, optical coatings, and multiple manufacturing processes coalesced to produce a truly outstanding HD studio lens.
The many attributes of optical image quality that have benefited from this totally new design are as follows:
New glass materials and contemporary design strategies have achieved an exceptionally high MTF at picture center and at image extremities.
New multilayer anti-reflection optical coatings provide even greater control over internal reflections and flare to produce superb black reproduction.
The deployment of new glass materials and the multilayer coatings on every lens element surface have elevated the overall transmittance of the lens while also shaping its spectral response to optimize the HD lens-camera color gamut.
New design techniques and innovative deployment of many different glass materials has significantly reduced both longitudinal and lateral chromatic aberrations across the entire focal range of the lens. Lateral chromatic aberration is exceptionally low over the entire focal range.
At the widest angle of 6.5mm the lens manifest a tightly controlled barrel distortion that is subjectively not discernible. The low pincushion distortion across the majority of the focal range is virtually invisible.
Relative Light Distribution
The falloff in image brightness from picture center to extremities inherent within all lenses has been minimized by employment of large glass and optical compensation techniques. Over the aperture range from wide open typical to studio shooting, the brightness across the 16:9 image plane is superbly controlled – ensuring an excellent contrast ratio over the entire picture.
Management of Strong Light Sources
Capitalizing on extensive global experiences with our predecessor HD studio lens, a variety of innovative strategies were mobilized to closely control the ghosting and veiling flare artifacts that can be stimulated by unusually strong light sources within a scene.
The Challenge of an HDTV Auto Focus System
HDTV inherently implies a smaller “permissible circle of confusion” than that of SDTV. This significantly heightens the sensitivity of the lens focus control and demands continuing close attention on the part of the camera operator. As they contend with the task of framing HD images and manipulating camera movements the multi-tasking pressures are elevated by this need for unrelenting vigilance in maintaining sharp focus. This is especially challenging in the field when shooting fast moving subjects within a busy scene (as on a sports field).
In 2007 Canon introduced a novel new auto focus system integrated into an HDTV long-zoom field lens that utilizes specially developed AF sensors providing very fast information relating to the momentary position of a rapidly moving subject within a larger scene.
A variant on this system has now been developed for the unique needs of the HDTV studio lens.
The Special Needs of HD Focus within the Studio Environment
The studio environment poses its own special focusing challenges to the HDTV camera operator. The depth of field can become unusually short when imaging in the relatively low illuminations seen today in many contemporary studios. For example, for a 2/3-inch HD lens camera system, depth of field is less than 18 inches when the lens aperture is set to F2.8, focal length to 25mm, and a subject is 15 feet from the lens front. Under such conditions, departure from a sharp focus can be encountered with a mere six inches of subject movement. Thus, the unexpected movements of news anchors and talk show participants can easily cause a momentary defocus. In the critical environment of a home shopping show, unpredictable movements of show hosts and models (and especially the wares being portrayed) can impair HD lens focus.
Separately, the growing interest in integrated HD news studios has spawned the development of very sophisticated automation and robotic systems that encompass the multi-faceted operational dynamics of managing multiple video and audio sources, graphics, production switcher and effects – and, studio cameras and lens controls. Automating the focus control of those lenses can be a major contribution to streamlining the automation of this highly complex production environment.
New Studio Auto Focus Lens
Canon is introducing its first auto focus system built into an HD studio lens – the new XJ27x6.5B AF. It utilizes the same technology as the HDTV field lenses. However, the calculating algorithm and the control software have been separately optimized for the shootings conditions that typify studio production.