By Jeff Kabachinski, MS-T, BS-ETE, MCNE
I should have known that televisions and PC monitors would only get bigger with higher resolution as time passed. After seeing ads for the new ultra high definition (UHD) technology, I wanted to know more about how it might affect healthcare. I think that the eventual payoff will be better screens to see diagnostic imaging details and large UHD screens for central patient monitoring stations in care units. This installment of Networking takes a look at a few of the technical details behind UHD and offers a few tips for the end user.
At first glance, it seems that the UHD technology, also known as 4K, can only build us bigger HD screens. I know that a 145-inch display (a 12-footer!) was built in the lab a few years back,1 but since December 2013, a 110-inch 4K HDTV (a mere 9-footer) has been commercially available from Samsung. As we’ll see, 8K HD and 16K HD can get us even larger displays at top resolutions.
Currently, UHD generally refers to 4K HD or approximately 4,000 lines, four times the resolution of HD at 1080p (the letter p in 1080p denotes a progressive scan). 1080i had an interlaced scan, where the monitor or TV would project or light up every other pixel row per scan, therefore needing two scans to complete the image. This approach was modeled after older TV specs. As long as the entire screen can be updated within 16.67 ms (60 Hz), it will appear to the eye as a static picture. This should be no surprise—after all, an incandescent light bulb flashes at 60 Hz, and it seems like a steady light to us. Even so, modern televisions scan at 120 Hz, with some stepping up to 240 Hz.
For consumer televisions, 4K HDTV is usually called simply UHD. However, UHD really encompasses at least three levels of resolution. As shown in the table above, other levels include 8K HDTV, known as Full UHD, and 16K HDTV, known as Quad UHD. The number of pixels for each type of resolution increase correspondingly, up to 132 megapixels.
The problem at the moment, of course, is that there is not a lot of content currently available for UHD. It takes a lot of devices and a high level of technology to build the images and then be able to stream 8 megapixels of data at least every 16 ms.
“There are universal needs across all verticals when it comes to the 4K production chain in pro AV,” says Chris Chinnock, president at analyst firm Insight Media. “You must have cameras or an acquisition system to gather the content; you need a processing and editing capability to manage that content; you need a distribution system that’s part of the solution; a display system; and finally, there’s lot of other pieces of hardware for encoding,” he says. “You must have all those pieces in place if you want native 4K.”2
In terms of moving all that data, the Wireless Gigabit Alliance (WiGig) specification of 7 Gbps in the unlicensed 60GHz range (IEEE802.11ad) has successfully been used to stream UHD.3 The pieces are coming into place!
The March 2014 issue of Consumer Reports suggests that for most users, the 1080p screens are fine. The new, higher resolutions produce a very sharp image with fine detail, but it’s tough to appreciate the difference unless you’ve got an 80-inch or larger screen or are sitting very close to a smaller one. The 1080p units that they tested in general had better all-around clarity and picture than UHD sets.4
Some observers predict that 4K HDTV will shortly displace 3D as the preferred home theater experience.5 Incidentally, 4K HDTV calls for 22.2 surround sound technology. That’s 22 surrounding speakers and two sub-woofers, the first six of which are the same as Dolby 5.1. And you thought you were finished building your home theater!
Another aspect of the new resolution is the added color range it brings. The specification identified as International Telecommunication Union Recommendation (ITU-R) BT2020, or Rec 2020 for short, was released on August 23, 2012. It defines the color space or range for UHD TV. The Rec. 2020 (UHD) color range can reproduce colors that cannot be shown with the Rec. 709 (HDTV) color range.6
The range of the colors we can see was defined years ago in another spec known as the CIE 1931 Color Space. It comes from the International Commission on Illumination (CIE) and its study of color perception of the human eye. Rec 2020 (UHD) color space covers 76% of CIE 1931, the digital cinema reference projector color space covers about 54%, the Adobe RGB color space covers 52%, and the Rec 709 (HD) color space covers 36%.1
But all that color and all those pixels don’t speak to the resolution in terms of pixel density. As I started to investigate pixel density, I wondered, what can the human eye really see? We don’t need screen resolutions to go beyond our ability to resolve the picture quality.
It turns out that mostly it depends on your eyes and the distance of the object under observation. Steve Jobs said that the iPhone (the 4S at the time) had a display that was so fine in terms of pixel density that it was beyond our capacity to see any clearer. He may have been right. Jobs indicated that the magic number is 300 pixels per inch (ppi) from a distance of 10 to 12 inches.
The bottom line is how well we can see. Research indicates that the highest resolution we can perceive is 477 ppi at a distance of about 10 inches. However, that’s for the best possible human eyesight and mechanical ability of the perfect eye. Normal, 20/20 vision resolves to about 286 ppi. So Jobs may have been right, since the iPhone resolution is 326 ppi.
Another way to look at it is in terms of sight angle. Perfect vision can see detail down to 0.6 arcmins (60 arcmins per degree—see sidebar). To get an idea of what this means, consider that the full moon is about a half a degree wide in the sky, or 30 arcmins, while 20/20 vision can distinguish about 1 arcmin.7
All in all, it will take a few years before 4K HDTV becomes the norm and 4K content is commonplace. Be aware that it may be best to consider the ppi and your usual viewing distance. Pixels are essentially imperceptible at around 300 ppi from a distance of 10 to 12 inches. Since that density is currently available in smart phones, it won’t be long until we see it showing up in healthcare. In the future, as 16K HDTV becomes available, the radiologist will be able to sit a foot away from the screen and zoom into the image for greater physiological detail while maintaining maximum clarity. Then we’ll be getting somewhere! 24×7
Jeff Kabachinski is the director of technical development for Aramark Healthcare Technologies in Charlotte, NC. For more information, contact [email protected].
Sidebar: Resolving 0.6 Arcmins
To get a better perspective on what Ultra High Definition means, let’s run a few numbers. At 0.6 arcmins, you’ll get to the magic scale factor of 5,730 for the human eye. In other words, at a resolution of 0.6 arcmins, something a foot long will appear to be a dot (unresolved) at 5,730 feet away. Closer than that, and we’ll be able to distinguish that it is an elongated image.
Divide the size of the object by 5,730 to get the distance at which an object will be unresolved. So for a foot away, 12 inches divided by 5730 equals 0.0021 inches. If the pixels are smaller than that, we won’t be able to distinguish them individually. However, normal 20/20 vision is closer to 1 arcmin, or a magic scale factor of 3,438. That changes our pixel calculation to 0.0035, making Jobs correct in his assessment! 7
1. Ultra high definition television. Available at: http://en.wikipedia.org/wiki/Ultra_high_definition_television. Accessed January 20, 2014.
2. Heck M. (2013, June). Is 4K Hype or the Next Big Thing in Pro AV? Available at: http://www.infocomm.org/cps/rde/xchg/infocomm/hs.xsl/37046.htm. Accessed January 21, 2014.
3. Mearian L. (2013, September 12). Bandwidth alert: It’s now possible to wirelessly stream 4K video. Available at: http://www.computerworld.com/s/article/9242377/Bandwidth_alert_It_s_now_possible_to_wirelessly_stream_4K_video. Accessed January 21, 2014.
4. Best deals on TV ultimate entertainment guide. Consumer Reports. March 2014:37.
5. New! Ultra High Definition TFTs (4k). Available at: http://www.usmicroproducts.com/displays/tft/4k. Accessed January 19, 2014.
6. Rec 2020. (2014, January 26). Available at: http://en.wikipedia.org/wiki/Rec._2020. Accessed January 28, 2014.
7. Platt P. Resolving the iPhone resolution. Available at: http://blogs.discovermagazine.com/badastronomy/2010/06/10/resolving-the-iphone-resolution. Accessed January 28, 2014.