UHD + (5120 × 2160) resolution screens explanation
So, some manufacturers, for example, Samsung display, produce 5120×2160 resolution displays which they designate as UHD +.
UHD vs UHD +
What is the difference between such a display and a standard display with resolution (3840×2160). It is clear that if you compare the UHD display against UHD +, there are more points along the horizontal. So what do we know about reproducing a color image. In the video, a color image is created from three colors of red, blue, green. The combination of these three colors creates a palette of color shades. If you divide 3840 by 3, we get 1280 pixels of the same color.
But there are screen designs when a single color pixel is added horizontally. This is usually a white pixel, it is added to increase the brightness of the image.
As a result, one color has 3840/4 = 960 pixels and, in principle, such screens cannot be called UHD. Such displays when displaying UHD video simply do not show part of the pixels from the video. Rather, the processor when processing such a video using a special algorithm shows only part of the pixels. More precisely, every fourth pixel is not shown. To really make the UHD RGBW display, pixels have been added horizontally. 5120/4 = 1280 pixels of the same color. In UHD + displays, when displaying UHD video, each pixel in the video on the screen has its own pixel.
UHD + is a true UHD resolution display. But oddly enough, such displays are not widespread. The possible reason is that the viewer will not see the difference between the UHD and UHD + screens. And when a lower resolution video is shown on a UHD TV, this is not critical at all, since the image is scaled.