OnePlus 6 Display Analysis: Playing Bi-annual Catch-up

OnePlus 6 Display Analysis: Playing Bi-annual Catch-up

While OnePlus handsets creep up in price year-after-year, we the consumers have rising expectations for “flagship-level” components from the former proudly-self-labeled “flagship killer.” The display is the portal to just about everything we use our phones for, and as such, it deserves to be one of the most criticized components for the price we pay. Although OnePlus hasn’t necessarily disappointed in this department in the past — we gave the OnePlus 5T a rave review, acclaiming the color accuracy of its calibrated color profiles, which we remorsefully had to revoke — every year is new grounds for judgment when they decide to test the limits on their new hardware and pricing. This time around, in 2018, a new trend has set out to “improve” on last year’s initiative to slimming down the display bezels, and that is, of course, the ever-polarizing “notch” as seen on the OnePlus 6.

OnePlus 6 Display Review

Technology

Slabbed beautifully on the front of the glass sandwich is a 19:9 6.28-inch “Optic” AMOLED display, sourced from Samsung, with 2280×1080 pixels, each set up in a PenTile Diamond Pixel array. The resolution paired with the screen size results in a pixel density of 402 pixels per inch, which is OnePlus’ first “improvement” in pixel density since the OnePlus 3. Besides the 6, every successor since has only had a mere 401 pixels per inch (take your time, OnePlus). However, some pixels are now lost to the physically-rounded corners (which OnePlus rounded in software in the 5T). The aesthetic was chosen by OnePlus to match the shape of the display with the curve of the smartphone chassis. In exchange for about an additional 2.5 square centimeters of screen, there exists a cut-out, or a “notch,” on the top of the display that is 2 centimeters in length and 0.5 centimeters in width (about 1 square centimeter in area), that houses the front-facing camera, the earpiece, the RGB notification LED, and the ambient light sensor.

The PenTile Diamond Pixel array provides intrinsic subpixel smoothing by its diamond pixel shape and lengthens panel longevity by including larger but fewer blue subpixels, which deteriorate more quickly than red and green subpixels. Consequently, displays with the PenTile subpixel layout have one-third fewer total subpixels than displays with the conventional striped RGB pixel pattern found on most LCDs. However, the PenTile subpixel arrangement exploits the human eyes’ greater color sensitivity for green, which appears more luminous than red and blue, and greater sensitivity for luminance than for color, by maintaining a one-to-one green subpixel-to-pixel ratio. This results in the PenTile display having approximately the same luma resolution as the more commonly used striped RGB displays, but potentially introducing color fringe as a tradeoff.

While the OnePlus 6 display has a lower pixel resolution than most other OLED PenTile displays in its generation, the screen appears mostly sharp at typical viewing distances (about one foot or 30 centimeters). However, color fringing can become visible on images upon keen inspection and closer-than-typical viewing distances, depending on the viewer’s eyesight. For normal 20/20 vision,  we calculated that pixels on the OnePlus 6 display are unresolvable past 12 inches.

Since the appearance of the cut-out at the top can be distracting to some users, OnePlus provides an option to black out the sides of the notch and makes it inaccessible for apps to fill, leaving the area as a subtle status bar “bezel.” It also rounds off the top edges of the new working screen area, with a border radius that is different than that found at the bottom of the screen. The option can be found under Settings → Display → Notch display.

OnePlus 6 Display Review

YouTube “zoomed-to-fill” does not fill into the OnePlus 6 notch area

Furthermore, fullscreen or immersive-mode apps are restricted from creeping into the notch area by default, even if the notch area is not being hidden. This is so apps like games and media that typically use up the entire display and/or are used in landscape are not greeted with a protruding cut-out on the side that clips content. Users that would prefer the cut-out in those apps have the option to toggle it for individual apps under Settings → Display → App display in fullscreen.

The OnePlus 6 also supports YouTube HDR and thankfully receives Widevine L1 certification for HD video playback in Netflix, an omission on the 5T that let out a fervid uproar from dissatisfied consumers.


Performance Summary

The panel that OnePlus uses in the 6, despite its mid-range price, is actually of stellar quality and binning, although the 1080p resolution is disappointing for a competitive smartphone with a PenTile OLED display in 2018. The display has excellent brightness uniformity and minimal shifting in brightness and in color for typical viewing angles. At more-obtuse angles, however, the display does begin to “rainbow out,” which is not usually exhibited by modern high-end OLED panels. The display is bright enough for sufficient viewing under direct sunlight, and the panel has an underlying potential to get even brighter than what it’s already capable of, which is not accessible to consumers for reasons unknown to us besides the obvious hit in battery consumption and organic emitter strain. However, those repercussions exist on Samsung smartphones as well, and all their devices tap into the high brightness mode just fine. The OnePlus 6 display also deals with darker scenes very well and does not noticeably clip near-black shades.

The colors on the Default display profile on the OnePlus 6 are vibrant and punchy, with a white point that leans on the cooler side. The calibrated display profiles are pretty accurate, but they appear warmer than standard. Although the chromaticities of the colors are accurate, the OnePlus 6 has a slightly higher display gamma than the standard that will result in a higher image contrast and somewhat-darker color tones. The Adaptive mode display profile is OnePlus’ solution to adapting the display color temperature to the ambient lighting, and while it is respectable in intention, the implementation is mediocre. The shift in color temperature is barely effective. They also removed the Sunlight Display from the Adaptive mode that was found on the OnePlus 5T that decreased the on-screen image contrast in certain apps for improved sunlight visibility.

We found the display to be just slightly more power-efficient than the OnePlus 5T display, although the difference is within possibility for experimental standard deviation. We trialed both devices multiple times and the results remained consistent every time. The difference, however, should not be noticeable.


Methodology

To obtain quantitative color data from the display, we staged device-specific input test patterns on the display and measured the resulting emission from the display using an i1Pro 2 spectrophotometer. The test patterns and device settings we used are corrected for various display characteristics and potential software implementations that can alter our desired measurements. Many other sites’ display analyses do not properly account for them, and consequently, their data could be inaccurate.

We measured the grayscale in steps of 5%, from 0% (black) to 100% (white). We reported the perceptual color error of white, along with the average correlated color temperature of the display. From the readings, we also derived the perceptual display gamma using a least-squares fit on the experimental gamma values of each step. This gamma value is more meaningful and true-to-experience than those that reported the gamma reading from display calibration software like CalMan, which averages the experimental gamma of each step instead for calibration data.

The colors that we target for our test patterns are derived from DisplayMate’s absolute color accuracy plots. The colors are spaced roughly evenly throughout the CIE 1976 chromaticity scale, which makes them excellent targets to assess the complete color reproduction capabilities of a display.

We will primarily be using the color difference measurement CIEDE2000 (shortened to ΔE) as a metric for chromatic accuracy. CIEDE2000 is the industry standard color difference metric proposed by the International Commission on Illumination (CIE) that best describes perceptually uniform differences between color. Other color difference metrics exist as well, such as the color difference Δu′v′ on the CIE 1976 chromaticity scale, but these metrics are inferior in perceptual uniformity when assessing for visual noticeability, as the threshold for visual noticeability between measured colors and target colors can vary wildly. For example, a color difference Δu′v′ of 0.010 is not visually noticeable for blue, but the same measured color difference for yellow is noticeable at a glance.

CIEDE2000 normally considers luminance error in its computation, since luminance is a necessary component to completely describe color. Including luminance error in ΔE is helpful for calibrating a display to a specific gamma and white level, but its aggregate value should not be used for assessing display performance. For that, chromaticity and luminance should be measured independently. This is because the human visual system interprets chromaticity and luminance separately, and their errors pertain to different display issues.

In general, when the measured color difference ΔE is above 3.0, the color difference can be visually noticed at a glance. When the measured color difference ΔE is between 1.0 and 2.3, the difference in color can only be noticed in diagnostic conditions (e.g. when the measured color and target color appear right next to the other on the display being measured), otherwise, the color difference is not visually noticeable and appears accurate. A measured color difference ΔE of 1.0 or less is said to be imperceptible, and the measured color appears indistinguishable from the target color even when adjacent to it.

Display power consumption is measured by the slope of the linear regression between device battery drain and display brightness. Battery drain is observed and averaged over three minutes at 20% steps of brightness and trialed multiple times while minimizing external sources of battery drain.


Brightness

When measuring the display performance of an OLED panel, it is important to understand how its technology differs from traditional LCD panels. Liquid-crystal displays, or LCDs, require a backlight to pass light through the liquid crystal layer to produce the colors that we see. An OLED panel is capable of having each of its individual subpixels emit their own light. This means that the OLED panel must share a certain amount of power to every lit pixel from its maximum allotment. Thus, the more subpixels that need to be lit up, the more that the panel’s power needs to be divided, and the less power that each subpixel receives.

The APL (average pixel level or average picture level) of an image on a display is the average relative brightness of each of the subpixels. As an example, a completely red, green, or blue image has an APL of 33%, since each image consists of completely lighting up only one of the three subpixels. The complete color mixtures cyan (green and blue), magenta (red and blue), or yellow (red and green) have an APL of 67%, and a full-white image that lights up all three subpixels has an APL of 100%. Finally, for OLED panels, the higher the total on-screen content APL, the lower the brightness of each of the lit pixels. LCD panels do not exhibit this characteristic, and because of it, they tend to be much brighter at higher APLs than OLED panels.

Our display brightness comparison charts compare the maximum display brightness of the OnePlus 6 relative to others displays that we have measured. The labels for the horizontal axis on the bottom of the chart represent the multipliers for the difference in perceived brightness relative to the OnePlus 6 display, which we fixed at “1×.” The values are logarithmically scaled according to Steven’s Power Law, using the exponent for the perceived brightness of a point source and scaled proportionally to the maximum brightness of the OnePlus 6 display. This is done because the human eye has a logarithmic response to perceived brightness. Other charts that present brightness values on a linear scale do not properly represent the difference in perceived brightness of the displays.

The OnePlus 6 performs very similarly to our Oneplus 5T in manual brightness performance. The panel is respectfully bright and slightly outshines most other OLED displays, but doesn’t quite reach the likes of Apple or Samsung. The display should appear just-okay — no more, no less — while viewed under harsh direct sunlight, and should be perfectly adequate in tamer conditions. However, just like with the 5T, buried in the display driver is a high brightness mode setting that pushes the voltage limits of the OnePlus 6’s OLED panel, which Samsung uses in their own displays under intense ambient lighting.

The OnePlus 6 does not enter high brightness mode automatically under intense lighting like Samsung smartphones. However, we were able to force the setting and measure its brightness on the OnePlus 6 display and the results are absolutely astonishing. With high brightness mode enabled, the OnePlus 6 display becomes among the brightest in the business, with a peak brightness of 625 cd/m² at 100% APL and an intense 818 cd/m² at 50% APL. It is still unknown to us exactly why OnePlus has left high brightness mode out, but it’s there and it allows the display brightness to reach new heights. The power analysis for high brightness mode is performed later in our Power Consumption section.


Gamma

The gamma of a display determines the overall contrast and lightness of the colors on the screen. The industry standard gamma for most displays follows a power function of 2.20. Higher display gamma powers will result in higher image contrast and darker color mixtures, which the film industry is progressing towards, but smartphones are viewed in many different lighting conditions where higher gamma powers are not appropriate. Our gamma plot below is a log-log representation of a color’s lightness as seen on the OnePlus 6 display vs. its associated input color intensity: Higher than the Standard 2.20 line means the color tone appears lighter, and lower than the Standard 2.20 line means the color tone appears darker. The axes are scaled logarithmically since the human eye has a logarithmic response to perceived brightness.

The OnePlus 6 display has consistently darker color tones than standard across the intensity range, which is characteristic of OLED panels due to their dynamic luminance response to on-screen content APL. Reducing the luminance response to APL is the first critical step if display manufacturers want their OLED panels to approach the standard 2.20 gamma, although it comes with the consequence of lower peak display brightness. The OnePlus 6 display gamma of 2.35 is not too far from the standard, but it is noticeably darker. All the display profiles of the OnePlus 6 approximately share the same gamma curve. The OnePlus 6 also has great dark scene reproduction, with a black threshold of 0.4%, which is the maximum color intensity that is crushed to black. This is a small upgrade from the already-impressive 0.8% from the OnePlus 5T. For reference for those who are using (or who have used) the Google Pixel 2 XL, which is notorious for clipping blacks, the black threshold for its display on our unit is 8.6%.


Display Profiles

A device can come in a variety of different display profiles that can change the characteristics of the colors on the screen.

The OnePlus 6 shares the same four display profiles as its predecessor: Default, sRGB, DCI-P3, and Adaptive mode.

OnePlus 6 Display Review

The Default display profile, revealing by its label, is the display profile that the OnePlus 6 is set to by default. It outputs vibrant colors with a cold white point and is set out to impress by displaying general content with punchier colors. The profile does not adhere to any specific standard color gamut, not even to the outdated NTSC 1953 color gamut that others may have been led to believe by other reviewers.  It is the same color profile that OnePlus has used for their OnePlus 3, OnePlus 3T, OnePlus 5, and OnePlus 5T, and it is the same base color space that the Samsung Galaxy S7 targets in its Adaptive Display profile. The profile most closely matches a color space with NTSC red chromaticity, Adobe RGB/NTSC green chromaticity, and Rec.2020 blue chromaticity.

The sRGB display profile targets the standard RGB color space that almost all content is described in, and it is necessary to target as the default content color space for any color-accurate display. However, OnePlus does not include automatic color management in this display profile (or any of its others profiles), which is necessary to accurately render content that is described in other color spaces.

The DCI-P3 display profile maps all content colors to the P3 color space. Contrary to popular belief, this display profile cannot be considered accurate just because it conforms to a standard. Most content is described in the sRGB color space, and projecting them onto the P3 color space will oversaturate most content. This display profile will only accurate render content that contains colors described in the P3 color space, which generally is only HDR video, and certain images (newer iPhones can take P3 images, but they will not show on devices without proper software color transformation).

The Adaptive mode display profile is OnePlus’ take on Apple’s True Tone display, and has been changed from OnePlus’ previous version of Adaptive mode. The initial white balance is set close to the D65 standard, and the temperature of the white point changes based on the color of ambient light. However, the effect is very mild compared to Apple’s solution, and the Adaptive mode on the OnePlus 6 requires an intense light to trigger any noticeable difference. The “Sunlight display” on the OnePlus 5T that triggered on intense ambient light has been removed on the OnePlus 6’s revision of Adaptive mode, and the profile’s target color space is now based off of the Default display profile color space (with sRGB reds) instead of being based on the sRGB color space.

There is also a Custom color setting that allows the user to set the color temperature for the Default display profile, ranging from 5823K at its warmest to 8200k at its coldest.


Color Temperature

The average color temperature of a display determines how warm or how cold the colors look on the screen, most noticeably on lighter colors. A white point with a correlated color temperature of 6504K is considered the standard illuminant for the color of white and is necessary to target for accurate colors. Temperatures higher than 6504K are said to be cold, while temperatures lower than 6504K are warm. Regardless of the target color temperature of a display, ideally the color of white should remain consistent at any intensity, which would appear as a straight line in our chart below.

OnePlus 6 Display Review

The color temperature situation for the OnePlus 6 is quite troubling. The color temperature for the Default display profile is smooth and straight, while it is very jagged and inconsistent for the other display profiles, which hints at difficulty in calibration. The calibrated display profiles, sRGB and DCI-P3, are too warm, averaging around 6276K, while the Adaptive mode is a better fit at 6553K. OnePlus has been consistently calibrating the white point on their sRGB and DCI-P3 profiles too warm on their phones, which makes them appear very unappealing to those who care — or potentially care — about color accuracy since warmer white points tend to be regarded as looking “dirtied” or “aged”.


Color Accuracy

Our color accuracy plots provide readers a rough assessment of the color performance and calibration trends of a display. Shown below is the base for the color accuracy targets, plotted on the CIE 1976 chromaticity scale, with the circles representing the target colors.

OnePlus 6 Display Review

Reference sRGB color accuracy plots

The target color circles have a radius of 0.004, which is the distance of a just-noticeable color difference between two colors on the chart. Units of just-noticeable color differences are represented as white dots between the target color and the measured color, and one dot or more generally denotes a noticeable color difference. If there are no dots between a measured color and its target color, then the measured color can be safely assumed to appear accurate. If there are one or more white dots between the measured color and its target color, the measured color can still appear accurate depending on its color difference ΔE, which is a better indicator of visual noticeability than the Euclidean distances on the chart.

The colors in the sRGB display profile appear mostly accurate, with a just-noticeable warm white point color difference and only a few noticeable color errors. The OnePlus 6 sRGB display profile has a very accurate average color difference ΔE = 1.4 for the sRGB color space. It is a clear improvement over the 5T’s color accuracy performance (ΔE = 2.0), mainly due to its not-as-warm white point calibration.

When displaying P3 content, the OnePlus 6 display is sufficiently accurate in its DCI-P3 display profile. Unfortunately, the OnePlus 6 OLED display is lacking in its red emitter, which is noticeable in the upper half of its red saturation range for P3. Overall, the DCI-P3 display profile has an average color difference ΔE = 1.7 for the P3 color space. It needs to be reiterated that this display profile is only color-accurate for content described in the P3 color space. Most content is originally described in the sRGB color space, and for those, this profile will map out the colors and result in an inaccurate average color difference ΔE = 3.6.


Power Consumption

Relative to the OnePlus 5T display, the OnePlus 6 display consumes just about the same amount of power at 100% APL peak brightness, with the OnePlus 5T display consuming 1.64 watts and the OnePlus 6 display consuming 1.65 watts. The OnePlus 6 does have a larger screen area, however, and normalizing for both brightness and screen area we find that the OnePlus 6 outputs 2.51 candelas per watt compared to the OnePlus 5T’s output of 2.38 candelas per watt.

OLED panels emit light that is more intense the lower the on-screen APL, and because of that, they become more power-efficient at emitting intense light at lower APLs. At 50% APL, the OnePlus 6 emits 549 cd/m² with just 0.53 watts of power, which is much more effective than consuming 1.65 watts to emit 439 cd/m², although the area of emission is smaller for lower APLs. However, since APL is still a ratio of the original screen area, we can still normalize for its size along with the brightness. Maintaining 50% APL, the OnePlus 6 emits 10.1 candelas per watt, while the OnePlus 5T emits 9.82 candelas per watt.

The OnePlus 6 was found to include high brightness mode in its display driver, which we previously measured for peak brightness. There was a clear jump in the slope of power consumption switching from peak manual brightness to high brightness mode. By measuring its power consumption, we found that it consumed 3.19 watts for a fullscreen 100% APL peak brightness of 625 cd/m², or 1.84 candelas per watt. Trending at the OnePlus 6’s usual 2.51 candelas per watt for fullscreen peak brightness, it would theoretically only take 2.34 watts to reach 625 cd/m² following the same power efficacy, but it turns out to need 36% more power to be able to drive the panel to that limit-pushing fullscreen brightness. It is a significant amount of additional power, but we do not know if it is the reason why OnePlus has decided not to include it for consumers to tap in to.


Overview

Specification OnePlus 6 Notes
Display Type AMOLED, PenTile Diamond Pixel
Manufacturer Samsung
Display Size 5.7 inches by 2.7 inches

6.28 inches diagonally

Display Resolution 2280×1080 pixels Total number of pixels is slightly less due to rounded corners and display cut-out
Display Aspect Ratio 19:9 “Isn’t that just 2.11111111..:1?” Sure.
Pixel Density 402 pixels per inch Lower subpixel density due to PenTile Diamond Pixels
Subpixels Density 284 red subpixels per inch

402 green subpixels per inch

284 blue subpixels per inch

PenTile Diamond Pixel displays have fewer red and blue subpixels compared to green subpixels
Distance for Pixel Acuity <12.1 inches for color image

<8.6 inches for achromatic image

Distances for just-resolvable pixels with 20/20 vision. Typical smartphone viewing distance is about 12 inches
Peak Brightness 439 cd/m² at 100% APL

549 cd/m² at 50% APL

Maximum Display Power 1.65 watts Display power for emission at 100% APL peak brightness
Display Power Efficacy 2.51 cd/W at 100% APL

10.1 cd/W at 50% APL

Normalizes brightness and screen area.
Angular Brightness Shift -25% Measured at a 30-degree incline
Angular Color Shift ΔE = 4.8 Measured at a 30-degree incline
Black Threshold 0.4% Maximum color intensity to be clipped black, measured at 10 cd/m²
Specification Default sRGB DCI-P3 Adaptive Notes
Gamma 2.35

 

Slightly too high

2.35

 

Slightly too high

2.36

 

Slightly too high

2.37

 

Slightly too high

Ideally between 2.20–2.40
Correlated Color Temperature of White 7756K

 

Very cold by design

6248K

 

Too warm

6216K

 

Too warm

6592K

 

Changes according to ambient lighting

Standard is 6504K
Average Correlated Color Temperature 7285K

 

Cold by design

 

6277K

 

Too warm

6237K

 

Too warm

6553K

 

Changes according to ambient lighting

Standard is 6504K
White Point Color Difference ΔE = 7.9 ΔE = 2.3

 

Just noticeable

ΔE = 2.7 ΔE = 2.1

 

Appears accurate

Below 2.3 is accurate
Average Color Difference ΔE = 5.4

for sRGB color space

 

Oversaturated by design

ΔE = 1.4

for sRGB color space

 

Appears mostly accurate

ΔE = 1.7

for P3 color space


Not color managed; oversaturated by design

ΔE = 3.7

to sRGB color gamut

 

Oversaturated by design

Below 2.3 is accurate
Maximum Color Difference ΔE = 10.2

at 100% cyan-blue

for sRGB color space

ΔE = 4.4

at 100% cyan-blue

for sRGB color space

ΔE = 5.7

at 100% cyan-blue

for P3 color space

ΔE = 9.0

at 100% cyan-blue

Ideally below 2.3

Final Thoughts on the OnePlus 6 Display

To be brief, the display is not a whole lot different from the display found on the 5T. It is a very iterative upgrade, with small improvements across the board, and a new form factor. All the calibrations trends and display qualities remain similar to the 5T, with the biggest change being in the niche Adaptive mode display profile. While the 1080p resolution may seem fine to many, those who have used higher-density displays should feel that there is more to be desired from OnePlus after four iterations of 1080p PenTile OLED panels. As processors and display efficiency improve, and as the price of OnePlus phones increases, it is becoming inexcusable for OnePlus to not include higher-resolution displays on their smartphones. They are already alienating any consumer who wishes for a decent virtual reality experience. By creeping into “flagship” price territory, OnePlus now needs to acknowledge the higher expectations of those who buy expensive phones with high-density displays, and that they are now part of OnePlus’ potential user base. Also, it is still very upsetting that OnePlus does not include Android 8.0’s automatic color management into any of their display profiles, even if not many apps support it yet. As an advocate for accurate displays, automatic color management is a lot more important than many people may realize, but that’s a story for another day. Besides those, the display has almost every great quality that people want from a display. OnePlus seems to have handled the notch the best so far too, making it very minimal in size, by including the ability to hide it, and by preventing apps from being able to fill into it (though some apps, like Instagram, Snapchat and Facebook Messenger can still appear a bit glitchy). There are a lot of things to nitpick, but we think it would be hard to truly dissatisfy someone with the OnePlus 6 display — unless they just really hate the notch.

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