Beyond HD: What You Need to Know About 4K, UHD and QHD
“4K”, also called “Ultra High Definition” (UHD), has been the big trend recently in display technology, with product announcements and demonstrations from the world’s leading display manufacturers. At the same time, there has been a growing desire for higher resolution on the desktop, with well-publicized announcements of “Quad High Definition” (QHD) monitors. It’s easy to get lost in the alphabet soup, so here are a few things you need to know about these “beyond HD” resolution displays.
QHD monitors (or more accurately WQHD since the monitors are 16:9 aspect ratio widescreen formatted) boast a resolution of 2560 x 1440. QHD is four times the resolution of a 720p monitor (also called “HD”). QHD monitors are marketed for applications that require very detailed content or users who never want to see a pixel on their display. Applications include photography and video editing, CAD/CAM and other mechanical design, and big data visualization, where being able to “zoom in” without losing readability is critical. QHD monitors retail for less than $1,000, and the most common size is the 27-inch diagonal. (We recently introduced a 27-inch QHD monitor—the Planar PXL2790MW.)
UHD or 4K monitors deliver 3840 x 2160 resolution. Both QHD and UHD can be described as delivering “four times HD resolution,” but QHD uses 720p HD, while UDH uses full HD 1080p. When you count up the number of pixels in each display, a 4K monitor has 55 percent more pixels than a QHD monitor. The most common size you see today in this growing 4K category is the 84-inch diagonal.
One of the key selling features of these “beyond HD” resolution displays is pixel density. The number of pixels packed into a single square inch of the display makes a difference in applications where every detail counts. Calculating pixel density is straightforward: It’s simply the pixels in width and height divided by inches in width and height of the display itself. For instance, our 27-inch QHD monitor has a pixels per inch (PPI) density of around 108, and our UltraRes Series 84-inch 4K display has a PPI of 52. Both deliver stunning imagery at average viewing distances—even when you get up close, as anyone who has used such products can attest.
As AV professionals have long preached, viewing distance does play a role in whether or not individual pixels are perceivable. Even with the most sophisticated home theater systems, videophile enthusiasts couldn’t tell the difference between 720p and 1080p when sitting in the middle of their theater. But public venue, conference and desktop displays are viewed at much closer distances than what is recommended for movie theaters. So how can you make a smart choice with regard to “beyond HD” displays?
You may have heard consumer brands like Apple use the term “retina display”* to describe a screen on which your eye is unable to distinguish between pixels. In dots per inch, Apple has claimed the magic number to be 326, mirroring printing specifications that magazines have used for decades.
However, the full definition of this term is not only dependent on the pixels per inch, but also on the viewing distance and dot pitch of the display, which combine into a “pixels per degree” (PPD) calculation. Our engineers have calculated that with a viewing distance of around 5 feet from the display, a UltraRes Series 84-inch 4K display has the same pixels per degree as the Apple retina display on its popular devices. Similarly, our 27-inch QHD monitor, when viewed from a distance typical for desktop environments, is in this same pixels-per-degree range. In other words, according to these calculations, with reasonable viewing distance assumptions and native content, the pixels will be virtually imperceivable across displays.
Whether you’re navigating the world of resolution specifications or seeking the ultimate image experience, keeping the acronyms straight will help as you embark on the world beyond HD.
*The term “retina display” is a trademark of Apple Corp. and is only used here in reference to Apple’s approach.