Until recently, qualitatively converting images from standard to high-dynamic range (SDR to HDR) was only possible manually. But now IPI, imec’s Image Processing and Interpretation research group at the University of Ghent, has developed a unique set of algorithms to enable the high-quality, automatic conversion of images. In this article, Jan Aelterman, postdoctoral researcher, and Hiep Luong, project manager, tell us more about this groundbreaking technology.
About nits, HDR and SDR
200, 1,000 or 10,000 nits: anyone buying a new television set will shortly be faced with making a choice about the number of nits. The nit value indicates the maximum brightness, hence the brightest white on the screen. The nit value is expressed in cd/m2 (candela per square meter). The ‘dynamic range’ of a TV is the difference between the darkest black and the brightest white that the set can display at the same time. The more nits, the greater the ‘dynamic range’ and the closer the picture on the TV screen is able to approach reality. From 1,000 nits upward, we talk about “high dynamic range” or HDR. Or in the persuasive marketing terms of the shop display: “Ultra HD Premium”. HDR represents a significant quality improvement compared with the usual SDR television sets in our living rooms at the moment. The most advanced HDR prototypes currently have a range of 10,000 nits.
Jan Aelterman: “According to the trade press and media companies such as Netflix, the gain in quality going from SDR to HDR is far more important than the race for more pixels and higher resolution. HDR pictures are so close to reality that viewers even spontaneously experience depth, even though they are not watching a 3D program. In fact, HDR has nothing to do with depth.”