Glaring, overlit faces and blacked-out night-time backgrounds have ruined photographs, film and video ever since they were invented. Why can鈥檛 cameras just record things the way our eyes see them? Now a video system based on new data-crunching techniques means they can. 快猫短视频 explores what it will mean for the picture on your TV screen.
What鈥檚 new about it? HD video has been around for years
An easy mistake to make: this isn鈥檛 HD (high definition) 鈥� it鈥檚 HDR (high dynamic range).
Advertisement
What鈥檚 HDR, then?听听听听听听听
The dynamic range of an image is the difference in brightness between the lightest and darkest areas of the scene. Our eyes can handle a much wider range of brightnesses than conventional cameras and can adjust to sudden changes in light much more quickly. That鈥檚 why cameras often give under- or over-exposed images of scenes that were perfectly clear to the naked eye. HDR cameras get around this problem by taking a number of pictures at different exposures and combine them to give a more realistic depiction of a scene.
鈥淗DR is what we see every day of our lives,鈥� explains at the University of Warwick, UK, who worked on the new camera system.
Haven鈥檛 I seen this before?
The idea of combining images made at different exposure levels to enhance the realism of still photographs , but it鈥檚 only in the past decade that it has really taken off, as photographers use the internet to display their work and swap techniques. Check out the for a half-million or so examples.
These photos were made using software to combine several exposures taken one after another 鈥� using a tripod-mounted camera to make sure that the outlines of the images match. Many modern stills cameras such as the include settings to automatically adjust the exposure, and the Apple iPhone聽4 will capture three still images and combine them automatically to maximise dynamic range.
But what about HDR video?
Capturing HDR video involves continuously recording a scene at multiple exposure levels, a difficult technological challenge. Last September San Francisco-based studio created an HDR video (see video above) using a beam splitter that sent light from one scene to two EOS 5D Mk II cameras 鈥� which can record HD video 鈥� one of which was underexposed, the other overexposed. High-end movie camera manufacturer Red is .
Chalmers says that his system is better than these competitors, because it has the greatest range of exposure levels, or f-stops. 鈥淭wenty f-stops is a magic number, because it鈥檚 what the human eye can see,鈥� he explains. His team has also developed the first complete system for capturing, storing and displaying HDR images.
How does it work?
The camera in the new HDR system was developed by , based in Waldfischbach-Burgalben, Germany, and uses closely guarded proprietary technology. The company partnered with the University of Warwick to figure out how to store the vast amount of raw image data captured by the camera. 鈥淚t鈥檚 a CD鈥檚-worth of data a second,鈥� says Chalmers, but he has devised a compression method that can reduce this by a factor of 100 to 500, depending on the complexity of the scene.
Will I need a new TV to watch HDR video? I thought 3D was the next big thing.
You will need a new TV 鈥� not yet commercially available 鈥� to appreciate the full effect of HDR images, but Chalmers and his team are developing software to allow current TVs to display an HDR-enhanced picture. This could be applied to your existing TV with a firmware update or through a separate box. The HDR effect will complement 3D visuals, says Chalmers, because our eyes use lighting cues to perceive depth.
What else could HDR video be used for?
Besides the obvious attractions for the film and television industries, the new system could also help surgeons see what鈥檚 going on inside the body. Current cameras struggle with the contrast in brightness between the dark recesses of the body and light reflecting off shiny surgical tools, but HDR has no such problems. 鈥淭he blood actually looks blood-red,鈥� says Chalmers.
