Kill it before it lays eggs: On the Sony Xperia Z5 Premium's 4K UHD display and why it's useless

When it comes to display resolution, the law of diminishing returns pretty much renders any discussion moot. In essence, it states that, in most things, at some point further increases in X will results in smaller and smaller gains of Y. Put otherwise, the more you increase pixel count given an identical panel size, the less and less every other pixel will count, as you'll be reaching a fundamental limit—that of your eyes' finite resolving power. At the same time, these same pixels (of which you now have a ton) require extra processing time and thus drag down the efficiency of the entire system, whatever it might be: TV, tablet, or a smartphone. They're also more expensive to manufacture and cost extra if (or when) you shatter them and need to seek replacements.

It's an exceedingly simple relationship, and shouldn't be too hard for most people to grasp. And yet we continue to get flak here and there, with some of our readers claiming that we're unfair towards pixel-dense displays. The reality is that this isn't at all an emotional statement—it's just facts. When you have a 5- or even 5.5-inch device in your hands, that same fundamental limit mentioned earlier has already been reached by the industry for the most part. A 5-inch, 1080p screen will give you a plenty high pixel density, any more of which will not benefit image detail depth—especially if you're using your phone like a normal human, meaning about 12 inches (30 centimeters) away from your face or more. Given such distance and a display size of 5.5 inches, you're already zoomed out far enough to be incapable (or barely able, at best) to notice any increases in sharpness.

To really drive this point home, we thought we'd take the just ludicrous, 4K UHD (2160 x 3840) pixel screen of the Sony Xperia Z5 Premium, and see if there's any benefit of packing over 800 pixels per every inch in a screen the size of an adolescent boy's hand. And because the very notion of this benefiting you in any way is just so ridiculous, we're not even going to try and keep this intro spoiler-free: There is none (-ish, we'll address this later).

Test parameters

Okay, so you'll probably require some proof beyond us just telling you that we spent a ton of time comparing the image of the Sony Xperia Z5 Premium next to that of the LG G4 (5.5 inches, 1440 x 2560 pixels, or 538 ppi) and the OnePlus 2 (5.5 inches, 1080 x 1920 pixels, or 401 ppi), and so we went ahead and got some. Before we start, a few disclaimers, though.

First off, the Sony Xperia Z5 Premium's 4K UHD screen is only a 4K UHD screen when you're inside the built-in photo gallery and video players. Outside of these, the image is 1080 x 1920 pixels upscaled to 4K UHD, so unless you're checking out your camera roll or watching a video (with the built-in video player), the rest of the time you're getting a less detailed image than you would with a Quad HD (1440 x 2560) smartphone such as the LG G4. That's a pretty important consideration that we'll address in the conclusion.

Secondly, we used several of Sony's own, extremely high-res (2160 x 3840 to be exact) images that come pre-loaded on the Xperia Z5 Premium, supposedly for you to marvel at on the 4K UHD display. To capture what we see, we used a 20.2-megapixel Canon 6D DSLR with a Canon EF 100mm, f/2.8 Macro USM Lens. After having to deal with a ton of technical bottlenecks, we settled on just one test scenario:

  • a ~4-inch (10 cm) close-up, or the minimum focus distance, in order to show some improvement in detail

When viewing these, remember that what we're looking at today is solely detail, and not color reproduction or any such. We simply want to know whether a 4K UHD screen provides practical benefits in terms of detail depth in comparison to the conventional Quad HD and 1080p panels of the day, so try and don't get distracted by factors such as white balance and so on.

Finally, and this is by far the most important part, there's no fool-proof way for you to experience the actual images offered by these two resolutions. That's true for a number of reasons. For example, the display you're viewing through is unlikely to be a 4K UHD panel, so there's some loss in clarity as your (likely) 1080p screen tries to render a 4K UHD image. Also, due to limitations to our site's layout, there's simply no way for us to show you full-resolution samples. Even on video, we'd be making quite a few sacrifices, including the fact that YouTube (even in 4K UHD) butchers the bit rate of the footage to reduce size. In conclusion, we chose to go with the extreme crops below, which have been pulled out to show you some improvement in detail, and are absolutely limited to just that. In reality, even if you go for some pixel peeping, you won't have the magnification seen with these crops to appreciate the extra detail offered by a 4K UHD panel. 

4K vs 1440p (QHD) vs 1080p

While it's likely that you'd be able to tell the 1080p screen of the OnePlus 2 apart from the higher res ones of the two competing devices seen above, even at magnification as big as here, you might struggle telling the Quad HD display of the LG G4 from that of the Xperia Z5 Premium. Make a guess if you want, for we didn't label the above crops on purpose.

For those curious, the line-up goes like this (left to right): LG G4 (1440p), Xperia Z5 Premium (4K UHD), and OnePlus 2 (1080p). If you picked the G4, that's understandable—its screen is actually a bit overly sharpened. No more games, though, here are a few additional crop pulls that aim to exemplify the kind of improvement in detail you can expect (and that we were able to get with the gear we had on hand) if you have a bionic eye:

We could go on like this for quite a while, but we consider this to be a sufficient demonstration. In fact, due to moiré introduced by our own camera, this particular comparison benefits the Xperia Z5 Premium unfairly. Not all of what you see is the result of inferior resolution—some of it is caused by our camera's inability to resolve detail that fine. In any case, this little comparison should put an end to what is a ridiculous topic anyway: For 99.99% of the population, a 4K UHD display on your smartphone does little good.

For the sake of objectivity, we'll mention that one profound reason to want a 4K UHD display is virtual reality (VR), which has been trending lately, but is still an incredibly rare use case scenario. Besides, even if you were the nuttiest VR fan out there, you'd still find little use in the Z5 Premium, as the screen goes into 4K UHD mode only when viewing Sony's Album and Video apps. Were you to use a dedicated VR app or game, you wouldn't benefit, unless Sony allows developers to manually flip a switch. In fact, you'd be in a worse place than if you had a Quad HD phone, which is a Quad HD phone at all times.


One of the most common responses we get when we publish pieces like this one is anecdotal: "Remember when everybody used to laugh at the supposedly non-existent gains in detail from 720p to 1080p?". Well, the fact is that, due to the aforementioned law of diminishing returns, the 720p to 1080p jump was still within the limits of sensible. Consequently, the move from 1080p to 1440p (Quad HD) made sense only when talking really, really large (say 6 inches) displays, and even then the trade-off in battery and processing overhead is considerable enough for you to want to think hard. But from Quad HD to 4K UHD? It's simply nonsensical. You can't see the difference in the real world and it benefits user experience in no way.

No, scratch that, a 4K UHD screen on a smartphone is actually detrimental to the user experience, especially if we get to a point where it's always-on. System performance will take a massive hit, and so will battery life—already exemplified by our Xperia Z5 Premium battery test, which put it on equal footing with the 1080p Xperia Z5, despite having a battery with 530 mAh extra. Clearly, the screen is drawing a lot of power, even if it only upscales content (our battery test is entirely rendered in 1080p). Even worse yet, if you're really after high resolution, you're actually better off with a Quad HD smartphone, as you'll benefit from the slight increase in sharpness over a 1080p panel at all times instead of just when viewing photos and video.

In conclusion, while there's nothing wrong with technological advancements and makers experimenting with newer and newer tech, it's important to keep in mind that newer isn't always better. Fundamental limits exist, and at the end of the day, we ought to be asking ourselves if more really is more. And in this case, we're pretty confident that it isn't. 

Related phones

Xperia Z5 Premium
  • Display 5.5" 2160 x 3840 pixels
  • Camera 23 MP / 5 MP front
  • Processor Qualcomm Snapdragon 810, Octa-core, 2000 MHz
  • Storage 32 GB + microSDXC
  • Battery 3430 mAh(19.17h 3G talk time)



1. bistech

Posts: 59; Member since: Jul 23, 2015

Other company making useless features. Just copy apple all features maybe so sony can gain sale. Copy the 4.7 and 5.7 screen and 3d touch

16. meanestgenius

Posts: 22199; Member since: May 28, 2014

Apple doesn't offer a 5.7 inch screen device. The 6 Plus/6s Plus is 5.5 inches, and Apple followed Samsung and others into the realm of large screen handsets.

40. tedkord

Posts: 17397; Member since: Jun 17, 2009

Forgive him. With the mighty bezels, the iPhone plus is bigger than most 5.7 inch phones, so it's an easy mistake to make.

43. meanestgenius

Posts: 22199; Member since: May 28, 2014

Lmao! Too true.

44. catze86

Posts: 731; Member since: Dec 07, 2015

I still remember one commentator posting about Apple patent Smart Bezels. That is why Apple use huge bezels

101. Nexus4lifes

Posts: 297; Member since: Feb 13, 2014

bistech would be like- then copy the bezels too they are very useful...

122. aBoss

Posts: 164; Member since: Sep 15, 2014

4k is good for Virtual reality and screen sharpness. Just need 120hz

143. michaelny2001

Posts: 334; Member since: Aug 01, 2012

we don't need 4k screens, quad HD is more than enough, though 1080p is fine too. I wouldn't mind seeing some new shapes and designs though.

140. BradyCrack

Posts: 835; Member since: Dec 29, 2015

What are bezels bad?

78. Acer_Predator unregistered

2k looks best in zooming

113. engineer-1701d unregistered

this is when all the people that dont have qhd or 4k say i dont see any difference and the normal smart people say no s*&t you not using a 4k screen to read this on and its not a moving image.

121. rick_mobile

Posts: 358; Member since: Dec 13, 2010

I was about to s**t all over this article with some clinical Ophthalmology articles and some from DisplayMate and how the eye can distinguish detail at 5.5 inches in 700-800 ppi displays compared to lower resolution; ofcourse the bigger the dispaly the better. Maybe the current hardware is not very efficient with 4k displays but I'm looking forward to my first 4K phone. There are some good points. I guess according to the author I'm not a "normal human" for using VR or having very good close range vision where i can actually detect pixelation on high res displays.

136. razraptre

Posts: 168; Member since: Oct 21, 2014

You can detect pixelation on an HD phone screen? :/

148. rick_mobile

Posts: 358; Member since: Dec 13, 2010

If you look at a 2k image vs a 1080p image OR icon you can tell the higher ressolution one is usually smoother, you have to look closer, for VR this is very apparant. I have a QHD phone and it's very pixelated with VR. We need higher resolutions

164. pauliunas

Posts: 14; Member since: Jan 16, 2016

You poor fanboi ;)

2. lalalaman

Posts: 638; Member since: Aug 19, 2013

sony should use diamond shape pixel....there 4K look ridiculous against that QHD screen plus the was an article why QHD is useless and now everyone kinda wants saying that 4K is useless is useless

4. Chris.P

Posts: 567; Member since: Jun 27, 2013

Yeah, no.

24. protozeloz

Posts: 5396; Member since: Sep 16, 2010


66. lalalaman

Posts: 638; Member since: Aug 19, 2013

with VR on the rise some OEMs might want to jump in that wagon and how tech is always evolving,in next 5 years i see some 4K phones.... of course i fully agree that it's an over kill for a regular power users and most of us like me want FHD and not QHD on our phones(if screen is less than 6inch) because we want crazy batteries in our phones. as for the diamond shaped pixels, that's my opinion

74. lalalaman

Posts: 638; Member since: Aug 19, 2013

i mean they are gonna make 4K no matter what and yeah, u agreed on the first one.

70. zeeBomb

Posts: 2318; Member since: Aug 14, 2014


6. Arch_Fiend

Posts: 3951; Member since: Oct 03, 2015

QHD Is Useless, In Most Cases Anyway.

41. tedkord

Posts: 17397; Member since: Jun 17, 2009

No, it's not. It's sharper and clearer than FHD, even at 5 inch display sizes. Sure, you can get by with FHD, but when I'm paying $700+ for s device, I don't want it just getting by.

71. Xperia14

Posts: 1208; Member since: Sep 01, 2015

So is 4k.

80. Arch_Fiend

Posts: 3951; Member since: Oct 03, 2015

That Goes Without Saying My Friend.

130. epdm2be

Posts: 823; Member since: Apr 20, 2012

Nonetheless you all seem to forget that your 4K-phone works most o/t time in QHD. The full 4K-resolution is only available with ONLY 2 build-in apps. So 4K as implemented on the Z5-series is bollocks! In my own personal opinion I'd rather have 60frames per second at all times in FHD, including the most demanding games, than 40% less frames per second than last years models on a QHD-device (or UHD-device for matter). In fact a lot of games run much smoother on an S5 than on a new S6. I only expect 2016 models to have the grunt for better gfx performance at QHD then 2014 FHD-models. So IMHO it's better to skip the 2015 models... ALL of them. 2016 midrange models will be faster or just as fast as today's high end QHD-models. But because of more sensible FHD-screens used in these models gaming will be smoother. Watch my words.

137. razraptre

Posts: 168; Member since: Oct 21, 2014

It works mostly in 1080p upscaled

79. Arch_Fiend

Posts: 3951; Member since: Oct 03, 2015

The increase in sharpness is miniscule, my M8's screen is just as sharp as my S6 . And did you say clearer....... that's not true lol. Clearness has more to do with what kind of display tech is being used and how well the display is calibrated. in all fairness my S6's display is amazing but the credit goes to it being amoled, colors just pop and catch your eye, the blacks are deep and everything just looks better on amoled. To know the truth you would need to compare samsung's best FHD to their best QHD. Nobody is doing that tho because sam's best FHD display Is on their mid ranged A series devices. PA had good things to say about the A8's display even tho its 1080p at 5.7in.

96. tedkord

Posts: 17397; Member since: Jun 17, 2009

Depends on your eyesight. I had 20/18 vision, and the difference between 720p and 1080p was stark. The difference between 1080p and 1440p was noticeable on high detail images, but not nearly as stark. Clarity is a function of sharpness. Again, you can get by at 1080p. Heck, you can even get by at 720p. For the price I'm paying, I want the best. I've got that right now in the Note 5 screen, which not only has some of the best sharpness, but also is tops in contrast, color and brightness (which are also important metrics in a display)

106. Arch_Fiend

Posts: 3951; Member since: Oct 03, 2015

20/20 Vision over here. I want the best to and I have that with the S6 but the best doesn't have to have QHD. What the hell was I saying, clarity and sharpness are the same damn thing lol. I'll admit QHD might benefit you more with your eyesight and the fact that your phone is 5.7in but I still believe the benefits of QHD over FHD is outweighed by the cons that QHD brings with it.

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