Display Measurement

Apple first introduced OLED panels in the iPhone X last year – and this year’s iPhone XS and XS Max are a continuation of the same designs. The XS’s panel ticks off all the features that are possible to have in a display – OLED, high resolution, wide gamut with colour management, and HDR display with official support of HDR10 and Dolby Vision. The panel is manufactured by Samsung Display, but is said to be a contracted design as blueprinted by Apple.

Among one of the questions I’m still asking myself, is who designed and is providing the display’s DDIC? OLED displays' DDICs are even more important than LCDs', because they not only control colour, but also have to control the active matrix power delivery, and thus the DACs that actually power on the individual pixels.

The iPhone’s display is still a scanning PWM powered panel, meaning the pixels are not actually continuously on, but pretty much work the same way a CRT beam would work – only instead of a single pixel, we have a partial vertical band across the display. The reason for this is just the sheer complexity of running the active-matrix: each subpixel needs to be controlled to 1024 voltage levels to represent the colours of the 10-bit panel. On top of that, the DACs need to have sufficient bit-depth to also provide a seamless range of brightness levels. Here saving on the DAC bit-depth by controlling brightness by PWM is a good workaround the issue.

The iPhone XS’ displays are really excellent at first sight, offering fantastic viewing angles. Personally however, I still have some reservation about the bezel design; Apple has been bested when it comes to screen-to-body ratio by other Android vendors, and I expect to see even more devices come out with what are true full device face screens.

The display’ pixel density doesn’t quite match other 1440p smartphones in terms of sharpness, but it’s still plenty sharp enough for the vast majority of people.

As always, we thank X-Rite and SpecraCal, as measurements are performed with an X-Rite i1Pro 2 spectrophotometer, with the exception of black levels which are measured with an i1Display Pro colorimeter. Data is collected and examined using SpectraCal's CalMAN software.


SpectraCal CalMAN
 XS  :      
XSM:      

In terms of greyscale accuracy, both the iPhone XS and iPhone XS Max present outstanding accuracy, coming in at an astonishing deltaE2000 of 0.79 for the XS and 1.64 for the XS Max. My Max unit seemed to lack intensity in the green channel, which reduced its accuracy score.

Both phones came in very close to the target 6500K of the D65 illumination point, in practice they’re very much perfect white.

Brightness wise, my XS maxed out at 646cd/m², while my XS Max came in at 668cd/m². There is no auto-brightness boost, however at such high brightness levels, there’s no need. Minimum brightness goes down to a little under 2 nits, allowing for comfortable night-time reading.


iPhone XS - iPhone XS Max
SpectraCal CalMAN

If one were to nit-pick, then it’s about the gamma measurement as the XS seemed to undershoot the 2.2 target, resulting in ever so slightly darker images, while my XS Max overshot it, resulting in brighter images. Still both were very much within imperceptible levels, so it’s not a great concern.


iPhone XS - iPhone XS Max
SpectraCal CalMAN

By default, the XS display and software interpret non-wide gamut tagged content as sRGB. Measuring the saturation accuracy here, we see some amazing results from both phones. The XS posted an amazing dE2000 of 0.79 – this is so low that it’s nigh-impossible to get much better, even when manually calibrating a display. The XS Max fared a bit worse at 0.95, but still below 1 which still deserves it the commendation of being excellently accurate.


iPhone XS - iPhone XS Max
SpectraCal CalMAN

When the application supports it, and the media has a wide gamut profile embedded, the iPhone XS displays are able to showcase the higher colour intensities of this wider colour gamut. Apple pretty much standardised “Display P3” in the mobile world – a display mode with the gamut of DCI P3, yet with an identical gamma target of 2.2 of sRGB, ensuring seamless interoperability of both gamuts within a display.

Again, both the iPhone XS and the XS Max showcase outstanding calibration with respective dE2000 of 1.19 and 1.03.


iPhone XS - iPhone XS Max
SpectraCal CalMAN


iPhone XS - iPhone XS Max
SpectraCal CalMAN

The Gretag Macbeth colour targets contain commonly encountered colours, such as skin tones and other colour samples. This test checks not only if the display is able to display the correct colour hue, but also the luminosity.

Again, the iPhones are able to show outstanding figures. The 0.74 score of the iPhone XS is I think the lowest figure we’ve measured on any kind of display, which is amazing. My XS Max figures scored a bit worse, it’s likely that the green channel weakness is part of what’s causing it to be better.

Overall, the iPhone displays are just outstanding. These are the best calibration results we’ve come to measure not only in a smartphone, but likely any display. I have literally nothing negative to say about them, and in terms of picture quality, they are just the best displays on the market.

Display Power

I was curious to see how the new XS fared against last year’s X – as it’s possible there might have been some under-the-hood improvements in terms of panel or emitter materials.

Unfortunately, it looks like the iPhone XS is nigh identical to the iPhone X when it comes to the power characteristics of the panel. My iPhone X had reached just a bit higher brightness and extended up the power curve a bit, but otherwise any differences can just as well be attributed to random manufacturing fluctuations.

Screen Luminance Power Efficiency
100% APL / White @ 200nits
Device Screen Luminance Power
at 200cd/m²
Luminance Power (mW) /
Screen area (cm²)
Efficiency
LG G7 257 mW 2.93
LG G6 363 mW 4.43
P20 411 mW 4.86
Galaxy S9 563 mW 6.69
P20 Pro 601 mW 6.74
Galaxy S8 590 mW 7.01
iPhone X ~671 mW ~8.31
iPhone XS ~736 mW ~9.11

Comparing the power efficiency at 200cd/m² and normalising the luminance power of the devices for their screen area, we see that the iPhone X and XS fall a tad behind other Samsung OLED panels. I think what this could be attributed to is the 10-bit colour depth of the Apple phones, as their DDIC and the active matrix would need to do more work versus the 8-bit counterparts.

One thing to also very much to take into account is the base power consumption of the phones. The iPhone X, XS and XS Max all fluctuate around 480-500 mW when on a black screen, which is around 150mW more than the iPhone 8 LCD models. This might not sound much, but’s it’s an absolutely huge figure when taking into account that it’s an unavoidable power consumption of the phone whenever the screen is on. I do hope Samsung and Apple alike would be able to focus more on optimising this, as like we’re about to see, it will have an impact on battery life.

GPU Performance & Power Battery Life
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  • alysdexia - Friday, May 10, 2019 - link

    ODEDs Reply
  • Henk Poley - Saturday, October 06, 2018 - link

    The OLEDs have a +41% higher pixel density as the LCD iPhones. So that's one reason why it could use more power. Reply
  • Constructor - Sunday, October 07, 2018 - link

    OLEDs are simply much, much less efficient than the crystalline LEDs used as LCD backlights. They only have an advantage when the image is mostly black, which just isn't the case almost anywhere on the web or elsewhere.

    And the OLED displays in the X/XS are PenTile, so red and blue only have half the nominal resolution. The indicated resolution actually applies to green only. But the GPU will probably need to work harder for the PenTile compensation algorithm.

    It still looks smudged to me especially at character edges (they're lined with tiny brownish/blueish pustules due to PenTile), and scrolling looks horribly janky, as if it was an old-time interlaced display, which is apparently due to the necessary PWM re-scanning.

    Neither of these püroblems exist with the excellent LCDs Apple has been using since the iPhone 6, which still have proper full-resolution RGB pixels and due to the LCD inertia scroll buttery smooth.

    So if any of the devices, it'll be the XR for me or none.
    Reply
  • Mic_whos_right - Tuesday, October 09, 2018 - link

    That makes sense. still. isn't the OLED designs suppose to use zero batt at times during black? Maybe for movie borders? Reply
  • Constructor - Tuesday, October 09, 2018 - link

    Yeah, I would also expect that the display controller should be able to go into low-power mode if it has all black pixels and it doesn't even need to scan in that state.

    Maybe there was some mistake in the measurement or the display wasn't actually completely black but just relatively dark with still some pixels on at lower brightness.

    It could also be that the controller needs some startup time so it might not be able to shut down unless it can really know for sure there won't suddenly be some bright pixels again.
    Reply
  • alysdexia - Friday, May 10, 2019 - link

    aren't, supposed Reply
  • wrkingclass_hero - Friday, October 05, 2018 - link

    I don't mind the minor typos, but I would have liked to have seen rec.2020 color gamut testing and sustained gameplay battery life. Reply
  • melgross - Saturday, October 06, 2018 - link

    Nobody has a rec2020 monitor, so there’s no point in testing for it. Reply
  • jameskatt - Saturday, October 06, 2018 - link

    Fantastic Review! But you missed the biggest item: The 8-Core Neural Processing Cores. These are used by Apple for Magic and huge acceleration of several tasks including realtime photo processing, Face ID, etc. These can be used in apps. The A12 has 18 cores - 2 Large CPU, 4 Small CPU, 4 GPU, and 8 NPU Cores. Reply
  • name99 - Saturday, October 06, 2018 - link

    If you're going to count like that, you need to throw in at least 7 Chinook cores (small 64-bit Apple-designed cores that act as controllers for various large blocks like the GPU or NPU).
    [A Chinook is a type of non-Vortex wind, just like a Zephyr, Tempest, or Mistral...]

    There's nothing that screams their existence on the die shots, but what little we know about them has been established by looking at the OS binaries for the new iPhones. Presumably if they really are minimal and require little to no L2 and smaller L1s (ie regular memory structures that are more easily visible), they could look like pretty much any of that vast sea of unexplained territory on the die.

    It's unclear what these do today apart from the obvious tasks like initialization and power tracking. (On the GPU it handles thread scheduling.)
    Even more interesting is what Apple's long term game here is? To move as much of the OS as possible off the main cores onto these auxiliary cores (and so the wheel of reincarnation spins back to System/360 Channel Controllers?) For example (in principle...) you could run the file system stack on the flash controller, or the network on a controller living near the radio basebands, and have the OS communicate with them at a much more abstract level.

    Does this make sense for power, performance, or security reasons? Not a clue! But in a world where transistors are cheap, I'm glad to see Apple slowly rethinking OS and system design decisions that were basically made in the early 1970s, and that we've stuck with ever since then regardless of tech changes.
    Reply

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