Smartphones with 4K/UHD screen, have we lost our minds or are they justified?

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The first smartphones with a 4K/UHD screen seem to be just around the corner. This possibility seems surprising if we have in mind that some users still aren’t sure if QHD screens for smartphones are necessary, especially if we consider its negative impact in the autonomy. Full HD screens still have an interesting way to go, but the clues seem to reveal that in high-range smartphones with screens above 5” they could be over soon.

It’s understandable that many users, including myself, are not attracted to this possibility due to the negative impact it could mean for the smartphones autonomy. However, there are other scenarios to look at to understand why some manufacturers are already working on smartphones with 4K/UHD screens. If you want to know all the clues, keep reading.

More than 5”, bigger resolution.

If the rumors going around the Internet during the last few weeks are true, this year we will experience a very clear tendency: the smartphones above 5”, at least the high-range models, will have their resolution slightly increased. Some days ago our partners from Xataka Android wrote about a leak on how after IFA, but probably before the end of the year, Sony will announce a new phablet called Xperia Z5 Plus.

Sharp and Everdisplay are two of the companies that have smartphones panels ready with 4K/UHD resolution

It’s important to keep in mind that this is a leak, and, therefore, there’s no guarantee this smartphone is coming with those features. But several sources, some of them have been right in the past, claim that it will have a screen with a 4K/UHD (2,160 x 3,840 pixels) resolution. An Asian source even claims that his smartphone will come with the 4K X-Reality Pro software to deliver the image scaling. That it’s the same we could find for a long time in the UHD Sony televisions. In any case, we will have to wait and see what happens.

A company supporting something like this is not enough to confirm a tendency. What’s relevant is the clues to believe that other manufacturers could follow the same path Sony seems to be on. Moreover, there are even tangible examples of companies with smartphone panels with 4K/UHD resolution, like Sharp. The latter showcased some time ago its IGZO LCD 5.5” panels. The Chinese Everdisplay has 6” 4K/UHD panels ready that reach a surprising density of 734 pixels per inch (in the Sharp panels it’s even bigger because they are smaller).

Do we need smartphones with 4K/UHD screens?

Leaving aside for the moment the issue of the effect on the autonomy of the smartphone, we can focus on its repercussion to our visual experience. As many of you remember, some weeks before the arrival of the first smartphones with QHD screens, we posted an article where we tried to analyze whether 1,440p panels were necessary and what do they bring to the game compared to the 1,080p panels.

The first conclusion was evident: a bigger resolution screen will bring a further level of detail. Because in order to put more pixels in the same screen you have to make them smaller, something that will make it harder for our eyes to perceive them individually. As a consequence, we will see images with of homogeneity and continuity. It will also be possible to gather details that would get lost if that same image was to be restored to a screen with a smaller resolution.

Our eyes “resolution”, in a healthy state, hovers around 530 ppp, according to Roger N. Clark

This idea could lead us to believe that, from the point of view of image quality, the more resolution a screen has, the better. But it’s not like that. The thing is our retina doesn’t have enough perception capacity for unlimited details. It has a finite resolution, and that’s why we won’t be able to appreciate the difference between two screens with a different definition. That will only be so if both are over the limits of perception in our visual system.

In this scenario, three different factors need to be considered: the size of the smartphone’s screen, its resolution and the viewing distance. Although the first you can be interconnected by introducing the pixels density per inch, so that we could use that parameter and the viewing distance. When it comes to the latter, many experts in smartphones agree that we normally place our phones at a distance from our eyes between 10 and 12 inches.

However, if we take a look at the literature from different researchers there are different data. Nevertheless, it’s worth taking a look. Raymond Soneira, from DisplayMate, claims that the real resolution of a healthy human retina is 0.6 arc minutes per pixel. However, J. Blackwell, from the Optical Society of America, established in 1946 that the human eye resolution gets close to 0.35 arc minutes.

In a conventional use scenario, the 4K/UHD don’t mean a tangible quality improvement against QHD screens

An angular unit of measurement that creates a relationship between the size of a pixel and the viewing distance. For most of us it’s a not very intuitive measure. Luckily we can turn to calculations by Roger N. Clark, a MIT researcher. According to this scientist, a healthy human eye (one that’s not afflicted by any visual handicap) can discern a maximum of 530 pixels per inch.

A 5” Full HD smartphone has a 441 pixels per inch density. Another one with the same size but with a QHD panel would reach the 590 pixels per inch. Taking Roger N. Clark’s calculations as a starting point, this indicated that the Full HD smartphones are below the perception limit of our eyes. Those smartphones with a QHD screen get close to it (as we already know, most of them have more than 5”, so that the density will be less than the 590ppp mentioned before).

In a real scenario, a lot of users are unable to appreciate the pixels in a 5” Full HD smartphone. Nevertheless, if we accept Roger N. Clark’s calculations, QHD screens make sense in terms of our visual experience. From this point of view, the 734 pixels per inch from the 6” 4K/UHD screens shown by Everdisplay don’t bring absolutely anything new to the table against the QHD panels because both are over the perception limits of our visual system.

The resolution conditions the performance

The reason why a smartphone with big resolution has an inferior autonomy compared to another smartphone with similar features and a smaller panel is directly related to the calculation effort that the SoC’s graphics logic has to run to process all those pixels. The more pixels has the screen, the bigger the effort for the SoC. Consequently, more energy from the battery will be needed.

Unfortunately, we all know that the battery technology isn’t evolving at the same rate as the smartphone panels. The arrival of the 4K/UHD screens could be worrying regarding autonomy (we wish we are wrong, and the manufacturers were to surprise us).

SoC’s graphics logic integrated in a 4K/UHD smartphone needs to process no less than 8,294,400 pixels

However, something to keep in mind is that the performance drop isn’t proportional to the increment the number of pixels in the screen. Luckily. A Full HD panel has a total of 2,073,600 pixels, whereas a QHD gets to 3,686,400 pixels. 4K/UHD panels will get up to 8,294,400 pixels. If we compared Full HD and UHD panels, we could observe how the number of pixels of the latter is four times that of the first. That could lead us to think that if they are in two smartphones with similar features, the performance from the one with the 4K/UHD screen will be four times reduced. But it’s not like that.

The difference is noticeable, and the Full HD has a better performance because the SoC has to process fewer pixels. But the difference here is not as big as it could had been expected. Nevertheless, it’s a fact to keep in mind.

Virtual reality: that could be the key

As we have seen, the common viewing distance nowadays is more than enough with the QHD screens (and also for many of us with the Full-HD panels). However, there’s a use scenario where Full HD and QHD resolutions in current smartphones might not be enough: virtual reality. The experience we get from our smartphone when placed just a few inches away from our eyes, for example, in the glasses Google Cardboard or the Samsung Gear VR, could clearly profit from this resolution increment.

We should have in mind that when we introduce a smartphone in these glasses each of our eyes perceives an image with the half of the panel columns. That means that if we use a Full HD smartphone we will get an effective resolution per eye of 960 x 1,280 pixels. These will increase up to 1,280 x 1,440 per eye with QHD screens. However, if we go for a smartphone with a 4K/UHD screen the resolution per eye will increase up to 1,920 x 2,160 pixels, so that the difference is important here.

Some months ago we had the chance to [try the Samsung Gear VR with a Galaxy Note 4(, which, as you may know, comes with a QHD screen (1,440 x 2,560 pixels). We got good feelings from this experience because of the high sharpness that didn’t cloud our perception of the stereoscopic images. However, at this short viewing distance the pixels could be slightly appreciated. So here a smartphone with a 4K/UHD screen would had probably delivered a more successful experience.

Beyond virtual reality

Can the virtual reality be the only reason that justifies the arrival of 4K/UHD smartphones even if it has a negative impact on the autonomy? The answer to this question depends on the user. For those who are curious about VR and wish to give it try, probably yes. However, jumping into the 4K/UHD resolution doesn’t seem to be alluring enough for the users who aren’t interested in VR.

Nonetheless, there’s yet another scenario where the 4K/UHD resolution arrival to the smartphones could have something to say: recording and playing 4K/UHD video. During the last two years, enough high-range smartphones have arrived with a feature to record 4K/UHD video. However, at best, the screen has a QHD resolution, or just doesn’t have a Full HD one. This means that when the taken video is played, we have to content ourselves with an downscaled viewing to adapt it to the native resolution of the screen, which is inferior to the one the video has been recorded into.

To be able to play video with the original quality and level of detail in the smartphone is something positive. But at the same time it isn’t something critical because a screen between 5 and 6 inches doesn’t have enough space to let us thoroughly view the video. The same thing happens with the possibility of using the 4K/UHD screens as an external monitor where we can monitor and reproduce the 4K/UHD video recorded with a camera. There’s no doubt it’s an interesting possibility, but it isn’t probably decisive for the reasons explained in the first lines of this paragraph. Even so, once we get in contact with one of these smartphones we will deeply test it and tell you our first impressions.

Before finishing this entry, we shouldn’t forget something we all already know. The reason behind tech manufacturers are making efforts to introduce innovative features in each new generation of products. Innovation is the real engine of the tech market, and the smartphones are not immune. A very effective strategy to encourage users to renew their terminals consists of introducing appealing features in the new models.

Sometimes those new features aren’t meant for the majority of users, but it’s still too early to predict how big virtual reality will be when it comes to the smartphones. Even so, we still have to wait for the first smartphones with 4K/UHD to get to the market. We will, of course, keep you updated.

Eye’s image | Rob Walker

Originally published at on January 1, 2015.