May 09, 2011

HDR with 20 stops of latitude

Researchers at the University of Warwick have been working on a High Dynamic Range video camera that creates imagery more representative of real world lighting.

If you include the eye's ability to quickly adapt to changing lighting conditions (automatically adjust its ISO rating in camera terms), we could be said to have a human dynamic range between light and dark of about 20 or 21 stops (although we can apparently only see about 6 or 7 at any given time). Cameras generally have a dynamic range of about 10 stops (up to 15 for the Arri Alexa or as much as 18 in HDRx mode on the Red Epic - pictured above).

The Warwick prototype camera (seen here recording thoracic surgery) can cope with 20 stops. As each stop represents a halving or doubling of light, this is impressive. Of course, recording this and then being able to display it are two different things, so they have also developed a new compression algorithm and a new HDR display (without the display it is still useful to have the dynamic range, but you just have to then adjust the exposure and contrast in post).

For the full story, read my article for TVB Europe magazine, including an interview with professor Alan Chalmers, head of the Visualisation Research group, at the university's WMG International Digital Laboratory (pictured top with the camera and display).

By David Fox

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