Sony stole the show at IFA by introducing the world’s first 4K display in a production smartphone, the Xperia Z5 Premium. The debate is still ongoing as to the practical use of the ridiculous 806ppi density, but there’s also been a fair share of skeptics claiming that the smartphone doesn’t even have an actual 4K panel and has a 1080p one instead.
The doubts have been additionally fueled by the fact that the most obvious way to ascertain the panel’s resolution – taking a screenshoot and checking the details, yields 1,080 x 1,920 pixel images. We did it too. Various apps we downloaded off the Play Store tell the same story - 1,080 x 1,776 pixels is the reported result, with the missing 144 pixels in height taken up by the on-screen buttons.
Out comes the microscope. What the software tried to fool us into believing, optics quickly exposed not to be the truth. Our shot reveals the teeny-tiny subpixels that comprise the Z5 Premium’s display, and there’s so many of them.
Expectedly, the subpixels are arranged in an RGB fashion, but a somewhat unorthodox one. Immediately noticeable is the herringbone pattern which changes direction every fourth row, with adjacent rows offset by a subpixel to either side.
That poses the question what happens to straight vertical lines, and the most obvious answer is some sort of subpixel rendering which employs neighboring pixels. It’s either that, or the resolution is simply so high that the subpixel arrangement doesn’t interfere with what you see with a naked eye.
We’ve also included our microscope shot of the OnePlus 2 here for comparison. It’s a 5.5-inch RGB panel too, but with “only” 1,080 x 1,920 pixels resolution, and its subpixels look huge compared to those of the Xperia Z5 Premium. The herringbone pattern is present too (as is, in fact, on most RGB LCD displays), only here it’s on a smaller scale – each row has its own slant, and the direction alternates with every row.
Which brings us back to the question of reported resolution. It’s entirely possible that Sony has opted to keep the interface rendered at 1080p most of the time for better efficiency, only switching to full-blown 4K when the displayed content requires it. We’re speculating here, but if the intended purpose of the display is indeed some sort of VR use, then the respective app might be able to trigger the screen to go into 2160p.
It’s also worth noting that we’ve been dissecting a pre-production unit with non-final software, so our findings may very well not apply to commercially available devices. For all we know, the retail units may be working in 4K full-time.
Hypotheses aside, the 2,160 x 3,840 pixels display of the Sony Xperia Z5 Premium is very much real.
Your original comment "So... it looks like Sony where unable to make it an actual 4K display, and went with fancy layout to mask that this screen has only 2/3 of required RGB subpixels. The individual subpixels are on a 1:2 grid instead of u...