QHD, HD, Full-HD, Quad-HD, 2K, Ultra-HD, 4K: What are the differences between them?
By Hamnet Azuma 2019-06-30 9213 0
Screen definition is an important factor to consider when talking about smartphone screens. As an indication, the larger the numbers, the better the result. The size of the screen (in inches), the number of pixels (the amount of information it can display) and the density of these pixels are grouped into this "definition" category (pixel per inch).
If you know the size of the screen, you can calculate the number of pixels compressed in a square inch: this is the number of pixels per inch (dpi), called pixel density. You can easily calculate the dpi of your phone using a pixel density calculator.
We have the main basics covered below, but we will start with an HD definition or higher, as this is what most smartphones currently offer. You may also want to pay attention to the "nits" indicated, which are an assessment of the brightness for the screens.
Explanation of the definition
Number of pixels (Horizontal x vertical)
4096 x 2160
4K, cinema 4K, True 4K
4K ultra HD
3840 x 2160
4K, ultra HD, 4K ultra HD
2560 x 1440
1920 x 1080
Full HD, FHD, HD High Definition
1280 x 720
HD, High Definition
HD stands for high definition. HD simply means a pixel measurement of 1280 x 720 pixels. Whatever the size of the screen, as long as the pixel measurement remains at this measurement, it is an HD screen.
As you can probably see, the smaller the HD screen, the higher the pixel density and, in theory, the better the image. Simply having an HD screen does not mean much, as it will produce a very different image on a 5-inch screen than on a 10-inch screen (note: the screen size is measured diagonally to take into account slightly different aspect ratios).
A 4.3-inch screen, for example, has a pixel density of 342 dpi. On a 4.7-inch screen, the pixel density drops to 312 dpi, but both are still HD screens. According to Apple, 300 dpi is the weak point, because it is about the point at which the human eye stops being able to discern individual pixels at a certain viewing distance (and on a screen of a certain size).
Full-HD is the next step and is currently the standard for screen definition for smartphones, although 2K (QHD) has gained ground over high-end devices.
Full-HD resolution measures 1920 x 1080 pixels. Again, the pixel density will depend on the overall size of the screen. With 5-inch smartphones, the pixel density is around 440 dpi, while on a 5.5-inch screen, this number drops to 400 dpi.
QHD, Quad HD or 2K
QHD stands for Quad HD, four times the standard HD definition. This means that you can insert the same number of pixels as four HD displays into a QHD display of the same size. The pixel measurement for QHD is 2560 x 1440 pixels. A 5.5-inch QHD display has a pixel density of 538 dpi. For comparison, the pixel density of a 5.5-inch Full-HD display is 400 dpi.
Definitions are also often referenced by the smallest number of pixels in the measurement - HD will sometimes be called 720p, Full HD is called 1080p and so on. With the QHD however, the name 2K comes from the fact that the largest of the pixel measurements is greater than 2000 pixels, which can certainly be a little confusing (and should really be called 2.5K, if we were quite accurate).
Many phones from Samsung, Motorola, Huawei and other leading mobile phone manufacturers include 2K displays as the standard today.
4K or Ultra HD
You can probably see where this is going. Like the 2K, the 4K name comes from the larger of the two pixel measurements, which are, technically speaking, 4096 pixels in 4K and only 3840 pixels in Ultra HD. Thus, although these two terms are often used interchangeably, they are actually a little different.
Ultra HD is 3860 x 2160 pixels and 4K is 4096 x 2160. Both definitions are often shortened to 2160p and the difference in pixels is relatively marginal, but there is a difference. The Sony Xperia Z5 Premium, which offers Ultra HD resolution on a 5.5-inch screen, was one of the first devices to be equipped with a'4K' screen.
Sony calls this screen 4K, but it actually uses the smaller measurement of Ultra HD, not the "real" 4K definition. Nevertheless, the Z5 Premium has a pixel density of 806 ppi - far beyond what many smartphones offer, and beyond what many people would say is necessary.
So, what definition to choose for which screen size?
Whether we're talking about entry-level, mid-level or high-end, users generally tend to focus on the larger features, which I understand. That being said, it is important to know that large numbers do not constitute quality.
Also be aware that the idea of choosing a screen with a smaller definition is not a bad thing since it will be less energy consuming than a screen with a higher definition. This is logical since its matrix concentrates fewer pixels. Perhaps this argument will change the minds of the big number pros and also slow down manufacturers in this crazy race.
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