For the critics of so-called "quad high definition" (QHD) (aka "2K") displays and the diminishing visual returns that come with them, avert your eyes. Japan's Sharp has unveiled a 5.5-inch display for smartphones that bumps the resolution to a mind-boggling 2,160 x 3,840 pixels. That's good enough to make this the world's first ultra-high definition (UHD) (aka "4K") smartphone display.
The density of the display measures in at an incredible 806 pixels per inch (ppi). As with the 4.1-inch, 736 ppi tiny "2K" display shown off last year, the new 4K display leverages Sharp's mature IGZO transparent semiconducting display technology.
The term IGZO refers to the elemental blend used to form the backplane of the pixels -- indium, gallium, zinc-oxide. The special semiconductor is pricier, but has helped sharp hit higher densities faster, as the electron mobility of IGZO is higher than amorphous silicon (a-Si), the cheaper alternative. That high mobilility allows the pixel density gains to keep pace with the die shrinks of the switching transistors.
The special panel not available yet, though. As per its typical process, Sharp is just shopping around demo units at present. Volume production is expected to start in late 2016, with a market rollout next holiday season or in early 2017.
That brings up the elephant in the room -- is 4K really necessary, even in a relatively large 5.5-inch smartphone display?
Aside from the cost of going to a 806 ppi density, the other downside to such a high display resolution is, of course, power consumption. Each pixel requires a separate set of transistors for the color components. Higher density displays use smaller transistors so each pixel is a bit more efficient. However, there's a lot more of them so the overall power consumption is likely to be modestly higher than even the previous QHD displays which -- as we saw -- were more power hungry than 1080p displays (necessitating beefier high capacity 2800+ mAh batteries).
The problem is that visually there may not be much to offset these downsides. People with very good vision can generally notice the improvement in sharpness moving from 1080p to a QHD display. But even those with 20/20 vision may have trouble telling the difference between a properly antialiased 5.5-inch display at 2K resolution versus a 4K display of the same size.
About the only sure-fire advantage will be the ability to display natively 4K video and image content. That could help people to better review the content they're generating and cut the power costs of such review (as no power-hungry downscaling conversions will be necessary). That in term could have a positive synergistic impact on generating UHD content for much larger displays, e.g. laptop and television displays -- niches where the visual difference of upgraded to 4K becomes truly visible.
In that regard synergy may be the strongest legitimate selling point of these bleeding edge super-high resolution displays. For better or worse, they'll likely be a big ticket item in the next year or so. Samsung has also shown 4K smartphone displays are on its upcoming roadmap, so Sharp will have competition in the near future.
In fact rumor has it that Samsung could unveil a 4K smartphone as early as Q4 2015, although it's kept more tight-lipped than Sharp on 4K display units.