Perfect Picture

A revolution in imaging, equivalent in its impact to the change from black and white to colour, is almost upon us, according to goHDR – a company specialising in High Dynamic Range video.

You're watching a football match on television. It is one of those days of intense sunlight and the ball is moving between areas of extreme brightness and deep darkness. Normally, this would cause huge challenges for those that are trying to film the proceedings – and deliver the high quality images viewers expect. But, on this occasion, everyone sits back and relaxes, knowing everything will be taken care of and that the pictures being beamed out to the watching millions will be immaculate, with all of the shadow and flare that often blight such occasions eliminated. Welcome to the world of High Dynamic Range video.

And the people everyone should be thanking for this breakthrough are the researchers at the University of Warwick, together with their partners goHDR and Altera Toronto Technology Center, the force behind the development of an embedded system that can be connected to existing televisions, allowing them to display High Dynamic Range (HDR) content.

This will bring a revolution in imaging, equivalent in its impact to the change from black and white to colour, according to goHDR. "The effect of this will be enormous," it asserts. "For example, the ability to clearly see the football when it is kicked from the shadow of a stadium into sunshine; surveillance cameras that can detect detail, even in extreme lighting conditions; or surgeons using video to conduct or record surgery."

goHDR – a company spun out of the University of Warwick by Prof Alan Chalmers – is a software business whose niche is to provide advanced data compression algorithms to all those who are developing HDR technology, with the goal of becoming the main player in the software that enables HDR video. "This project has brought together worldwide expertise in HDR imaging from the University of Warwick, with the innovation and in-depth market knowledge of goHDR and Altera," states Chalmers. "Together, the partners have demonstrated the technical and commercial viability of HDR-enabled television."

HDR video captures a wider range of light intensity levels found in real scenes, ranging from direct sunlight to low-light images. HDR imagery offers a significantly enhanced viewing experience, even when the higher contrasts are reduced (through appropriate luminance compression algorithms, known as tone mapping) for display on Low Dynamic Range (LDR) devices, such as in computer monitors or televisions. This enhanced experience allows the viewer to see clearly the details of a racing car when it enters or leaves a tunnel, for instance. Furthermore, the increased lighting of HDR content provides better depth perception, allowing a 3D viewing experience, without the need to wear special glasses.

"We have also recently successfully trialled its use to assist and document surgery," adds Chalmers, "together with the thoracic surgery team and the multi-media group at Heartlands Hospital [the flagship hospital of the Heart of England NHS Foundation Trust]. HDR is able to accurately capture for the first time the wide range of lighting present in an operation from the dark body cavities through to the bright highlights on the shiny medical instruments."

"The natural world presents us with a wide range of colours and intensities. In addition, a scene may be constantly changing with, for example, significant differences in lighting levels going from outside to inside or simply as the sun goes behind some clouds etc. A human eye can cope with those rapid changes and variety but a traditional camera is only capable of capturing a limited range of lighting in any scene. The actual range it can cope with depends on the exposure and f-stop setting of the camera. Anything outside that limited range is either under- or over-exposed."

"HDR imagery offers a more representative description of real-world lighting by storing data with a higher bit-depth per pixel than more conventional images. Although HDR imagery for static images has been around for 15 years, it has not been possible to capture HDR video until now. However, such HDR images are typically painstakingly created in computer graphics or generated from a number of static images, often merging only 4 exposures at different stops to build an HDR image.

"Our new HDR camera technology and software enables us to capture and display dynamic HDR images, covering at least 20 f-stops, at full high-definition resolution, and at 30 frames-per-second. Furthermore, HDR can complement 3D technology by providing depth perception without the need to wear 3D glasses."

The partners showcased the HDR-enabled TV at the IBC 2011 event in Amsterdam in September this year, one of the premier annual events for broadcast professionals, which attracts tens of thousands of people from around 140 countries annually. Engineering Careers editor Brian Wall was at the show and was much impressed by the technology. Along with a demonstration of a variety of HDR footage, the short film, 'Morgan Lovers', was screened and drew a large audience. The film was shot, manipulated and can be displayed entirely in HDR. It was a collaborative venture with local film maker Vermillion Films and Morgan Cars.

Television is at an exciting crossroads, says Chalmers. With High Definition (1920x1080 pixels resolution) finally being widely adopted, television manufacturers are now looking for the "next big thing". There are currently three possible options: 3D, superHD and HDR. Yet, despite the viewing enhancements that 3D and superHD bring about, both these systems fail to capture the full range of lighting in a real scene. This can result in under- or over-exposed pixels and thus missing content, he continues.

HDR is the third option. "This approach captures the full range of lighting in a scene," he asserts. "HDR can complement both 3D and superHD – ensuring no pixels are missing. The University of Warwick and goHDR are working hard to educate the market and show, through their HDR products and demonstrations, that High Dynamic Range will be the next 'big thing' in television."

Author
Brian Wall

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