The shift from SD to HD offered viewers such a dramatic improvement in video quality that “high-resolution” effectively became shorthand for better quality. This notion has helped to fuel 4K production and distribution, as well as the manufacture of a growing number of 4K television sets. As 4K content makes its way into the home, however, the format’s massive increase in pixels simply isn’t wowing audiences the way HD did.
As viewers first embraced HD, most also invested in a new HD TV that was much larger than their SD set. Those viewers now considering 4K-capable displays are looking at screen sizes similar to that of their existing HD TVs. Unless these viewers plan to reduce the distance from the sofa to the screen, the higher resolution of this new 4K display won’t greatly impact the viewing experience. What’s becoming clear is that other enhancements to image quality hold far more potential to wow viewers, and high dynamic range (HDR) is looking to be the technology that will make 4K — and even 2K — content awesomely beautiful to behold.
Two Kinds of HDR
There are two kinds of HDR: HDR for cameras and HDR for displays. They share the goal of making an image look more lifelike or better than it would be seen by the human eye, but they accomplish this goal in different ways.
HDR cameras bring out the best possible image by taking multiple shots at different exposures and combining the best of each to produce results that are incredibly rich. This technology has become so mainstream for still images that it is available in smartphone cameras. In contrast, HDR motion capture cameras have only recently emerged, in part because they require special-purpose electronics and software.
While HDR cameras can greatly improve picturequality by merging streams at different exposures, HDR-enabled TVstake it a step further bydisplaying a broader range of intensities for each pixel. These HDR displays give each pixel more depth for a broader range of values: the darks are darker, the brights are brighter,and there’s more fine-grained variation across the spectrum. More specifically, the move from the current 8-bit depth standardto a 10-bit depth for HDR TV expands color precision from 256 shades to 1023 shades.
HDR Requires More Storage
Improvements to image quality almost always come at a cost. Without compression, the jump from HD to 4K nearly quadruples storage requirements if both frame rates and pixel depth are kept constant. HDR demands additional storage capacity beyond that. First, HDR motion cameras capture two streams at different exposures, so they require twice the capacity for capture, ingest and editing storage. On top of that, creating and delivering 10-bit content for 4K displays requires an additional 25 percent at all stages of the workflow. And since most HDR cameras can capture in 16-bit, many content creators will likely choose to edit and archive in 16-bit instead of 10-bit for future-proofing. That means doubling capacity vs simply increasing 25 percent.
HDR Shines Where Higher Resolution Fades
While 4K and even larger formats generally require a larger screen size to prove effective, HDR’s advantages are plainly visible on a screen of any size. So, as leading media companies such as Netflix move to bring ever-greater realism to viewers’ screens, they are examining the improvements that HDR can bring to every pixel on that screen — in 2K or 4K. While 4K continues to be a primary focus for many content creators and providers, the stunning impact and much lower bandwidth requirement of HDR 2K content makes it a compelling alternative. Where 4K requires an extra 12 Mb/s or so of broadband speed for streaming,a 2K HDR stream can fit within the 10Mbps connection that many households have today, giving consumers a much improved viewing experience without upgrading their service.
HDR Now and in the Future
How quickly HDR content will be readily available remains to be seen. The good news is that HDR capabilities are making their way into 4K TVs that consumers can buy now, video streaming services are getting on board, and 4K displays generally do a good job up-rezzing from 2K. The bad news is that broadcast HDR content lags behind, largely because the U.S. broadcast system simply isn’t equipped to support either 4K or HDR.As more and more consumers adopt HDR-capable TVs;however, the momentum will likely pick up and fuel large-scale equipment and workflow upgradesto support HDR.
By radically boosting image qualityeven where bandwidth is limited, HDR has the greatest potential to deliver the beauty that’s widely expected of 4K.Viewers may not be able distinguish between more pixels and better pixels, but in the long runit may not matter. With the new Ultra HD standard, the industry candeliver both, provided the workflows for content creation and delivery are prepared.
