It’s nearing the end of 2019, and most smartphone makers have already showcased their flagship phone for this year. Google’s flagship comes in pretty late into the year, but in the tech world, a few months can mean a whole new generation of hardware capabilities.
However, the Pixels are not particularly known for their cutting-edge hardware — instead, they like to employ software to differentiate themselves, through useful optimizations and nifty features. For displays, the software side is typically limited to calibration and subjective accommodations, so this is where we expect Google to shine in.
Pixel 4 Display Review Highlights
- Shameful peak brightness that is dimmer than most other phones
- Improved black clipping compared to previous Pixel models, with notable significance in the Pixel 4
- Best total color accuracy measured in a smartphone
- Contrast/gamma inconsistencies in the Pixel 4 XL
- Higher grayscale color spread in the Pixel 4
- Novel, fluid 90Hz mobile display
- Best viewing angles on the Pixel 4
XDA DISPLAY GRADE
B
Last year, Google sourced their Pixel 3 display from LG while sourcing the Pixel 3 XL display from Samsung. Google continues the same panel sourcing this year, putting an LG display on the Pixel 4 while the Pixel 4 XL is equipped with a Samsung display. Unfortunately, neither phones are using current-generation OLED panels — the Samsung display on the Pixel 4 XL is the same one found on the OnePlus 7 Pro, which is a last-gen Samsung panel, and the Pixel 4 is using the same panel found on the Huawei Mate 30 Pro, which pales in comparison to Samsung’s latest display panels. Samsung’s current-generation display panels promote a new blue emitter material and an improvement in power efficiency and display brightness. Neither Pixel 4 device sees these benefits.
The two sizes also have different display pixel densities: the Pixel 4 has a pixel density of 444 pixels per inch (FHD+), while the larger Pixel 4 XL is sharper at 537 pixels per inch (QHD+). To my eyes, this difference is noticeable when viewing text. While the Google Pixel 4 does appear structurally sharp, I can sometimes make out red and green colors fringed next to text due to the OLED PenTile pixel arrangement. On the other hand, the Google Pixel 4 XL appears perfectly sharp, and I cannot make out color fringing no matter how close I am to the display. However, for most people, the lower resolution on the smaller Pixel 4 should not be an issue.
AmbientEQ
Google implemented a new dynamic display white balance system in the Pixel 4, called AmbientEQ, which uses the new RGB ambient light sensor to change the white balance of the display closer to the color temperature of the surrounding light. The goal of the feature is to make the display appear more like a naturally-reflective surface, like a piece of paper. The reason for this is that our perception of any given color changes depending on the color temperature of our surrounding environment. For example, the color of white on your smartphone may look significantly colder when viewed under warm, dim ambient lighting of some hipster restaurant. Changing the white balance of your display closer to that of the ambient lighting can help make your phone display appear more “natural” and easy on the eyes, as well as help it appear more consistent between different lighting conditions. The feature is a parallel to Apple’s True Tone feature. However, Google’s AmbientEQ is much more subtle than True Tone, and in my opinion, it is not nearly as effective as True Tone. AmbientEQ is limited between 6300 K and 7450 K display color temperatures, which is much more narrow than True Tone’s range. Google has also previously implemented AmbientEQ in their Home Hub display (now Nest Hub), and it works much better on that than it does on the Pixel 4. Fortunately, we are able to change the behavior of AmbientEQ and shape it to be more responsive to ambient lighting.
LG OLED viewing angles
Pixel 4 XL (left), Pixel 4 (right); Source: /u/zootia
One underappreciated aspect of the LG panel in the Pixel 4 is its viewing angles — LG OLEDs have the least color shift on any mobile OLED. Together with AmbientEQ and the Pixels’ flat display, the viewing angles really help improve their laminated “papery” appearance since the display doesn’t change colors at different angles. However, I do wish the Pixel 4 had a higher-resolution display, which would further improve the paper illusion.
The viewing angles on the Pixel 4 XL can tint slightly blue at moderate angles. However, it is on-par with the best on Samsung’s latest displays, which hasn’t changed much in the past few generations. I’m interested in knowing if the difference in viewing angles between the two vendors lies within the cavity design of the emitters or with the polarizer stack.
Smooth Display
And lastly, Google’s headling new feature for the Pixel 4 is its 90Hz “Smooth Display.” Higher refresh rates promote significant improvements in UI fluidity and touch response, and they are looking to become a bigger trend next year in the mobile market. However, no mobile OLED currently supports a variable refresh rate, and I think it is a mistake to implement a higher refresh rate system until variable refresh rate panels become available. For now, high refresh rate mobile OLEDs use discrete display modes for different refresh rates and use software to switch between higher and lower refresh rate display modes to conserve battery. The different display modes each require their own calibration tables, and they’re not likely to perfectly match with each other. These imperfections may be noticed when the display switches from one display mode to another, and Google’s software engineers have acknowledged this as a limitation of this software-based dynamic refresh rate system.
Display Profiles & Color Gamut
Color gamut for Google Pixel 4
The Google Pixel 4 has three different display profiles: Adaptive, Natural, and Boosted. All three profiles share the same white point, the same transfer characteristics, and they all support Android’s color management system.
The Adaptive profile is the default display profile of the Google Pixel 4. It is a color saturation-expanding profile that has increased vibrancy in reds and greens compared to standard sRGB. More precisely, red colors are measured to be about 10% more saturated, while greens are about 20% more saturated. Reds are also shifted slightly orange, while greens appear just slightly mintier. Blue colors receive no boost in saturation, but the adjusted primaries result in slightly lighter blue tones. It targets a standard 2.20 gamma and a D67 (6700 K) white point, like the other two profiles.
Updated Adaptive profile
On previous Pixel devices, the Adaptive profile did not support color management, but with the Pixel 4, Google has updated the Adaptive profile to support it. The new Adaptive profile now uses Display P3 as its composition color space, instead of sRGB remapped to a wider gamut. This allows the Adaptive profile to finally be consistent between different Pixel displays, and consistent in white point with the Natural and Boosted display profiles. For previous Pixel generations, this was not the case. As a result, both the Google Pixel 4 and Pixel 4 XL now have visually-identical Adaptive profiles, and the Natural and Adaptive profiles share white points. For color-managed content, the Adaptive profile maintains its rendering intent and renders the color-managed content with increased vibrancy. However, the Adaptive profile clips at P3 primaries, and it will clip high-saturation P3 content.
The Natural profile is the accurate display profile that follows industry standards (although internally targeting a D67 white point). This is the profile to use to get the most accurate colors out of the Google Pixel 4 display.
The Boosted profile is similar to the Natural profile, but it provides a slight boost in total color saturation. Google says that we perceive colors as less vibrant on smaller screens, like phones, which is their basis for the inclusion of this profile.
Pixel 4 Brightness
Comparative brightness chart
The Pixel devices have historically been unimpressive when it comes to display brightness. This year is no different. While every other major smartphone maker has made their OLEDs significantly brighter, Google has shown little-to-no progress. Google did manage to increase its newest phones’ brightness this year, from about 400 nits up to 450 nits, but it still leaves them as some of the dimmest flagship smartphones in recent years.
Lack of high brightness mode
The reason Google is so far behind is that they are refusing to incorporate a higher-power brightness state for their system brightness. Furthermore, Google is using last-generation display panels that cannot compete in power efficiency or in rated brightness with Samsung’s latest panels. What’s interesting is that Google has had a higher brightness mode within their phones, which they can tap into during HDR playback (or with root). But for reasons likely related to battery, Google does not allow their phones to use this extra brightness for normal use. Higher brightness modes do require significantly more power to drive — an 800-nit peak brightness state drains significantly more power than twice that of a 400-nit brightness state — but if the competition is able to support higher brightness levels and maintain better battery life than the Pixel devices, then Google is severely falling behind in both departments.
When enabling high brightness mode within the Pixel 4s’, their displays approach acceptable levels of brightness. At 600 nits, this ranks the Google Pixel 4 displays competitively with last years’ OLEDs in brightness. But in 2019, 600 nits is about the baseline for every major smartphone company, while the best are pushing 800 nits (100% APL). These are simply the limits of Google’s outdated panels, as the same panels found in the Huawei Mate 30 Pro and the OnePlus 7 Pro push the same brightness levels — except those phones actually push those brightness levels in normal use.
Camera viewfinder potential
As a company that focuses its phone marketing and identity on their camera, Google would benefit its campaign by having a brighter screen. This can help the camera experience by improving the accuracy of the viewfinder. The composition of a photo is a key factor of a good picture, which is aided primarily by what you see in the viewfinder. Google implemented Live HDR+ in the Pixel 4 viewfinder so that what you see before you take a picture looks closer to the picture that is captured and processed. However, during daylight shots, the viewfinder can look washed out if the display can’t get bright enough to accurately reproduce the scene. This is one of the key advantages of the optical viewfinders in SLRs, which shows the scene at the brightness and contrast that your eye would see. One other way that phone makers can improve their camera viewfinders is by using an absolute HDR viewfinder in the camera app, which would map the camera viewfinder on the phone display to the same absolute brightness as the scene.
Adjusted brightness response to APL
Last year, the DDIC in the Pixel 3 XL was adjusted to limit its brightness at lower emission levels (APL) to that of full-screen white (100% APL). While this may seem like a crippling move, it’s actually a necessary step for OLEDs so that they can have a consistent gamma calibration. The LG panel in the smaller Pixel 3 had a variable brightness response to APL, and it had an inaccurate and dramatically variant gamma range. Now with the new LG panel in the Pixel 4, it too has its lower emission brightness limited, so it should have significant improvements in gamma calibration. The Samsung panel in the Pixel 4 XL panel continues to retain this characteristic.
Pixel 4 Grayscale Accuracy
Grayscale plots for Pixel 4, 60Hz
Pixel phone displays have also been historically poor at grayscale consistency, often taking on a tint for darker colors and at lower display brightness. The calibration process at the factory can only fix so much, and can even make it worse. A display with a consistent grayscale can typically be attributed to tight OLED production tolerances and a mature fabrication process at the display manufacturing line. Google has a reputation for not providing the best quality control in their phones’ hardware, and for good reasons. The main offender has been the LG panels that Google has been using in their phones, and this year it’s a similar story. Google uses an LG panel for the smaller Pixel 4, and while it is a clear improvement over previous generations, it still shows a higher spread in its grayscale compared to some Samsung panels. The Google Pixel 4 XL uses a Samsung panel and clearly shows superior grayscale consistency in our plots above. Compared to the iPhone 11 Pro’s impeccable grayscale plots, however, there is still room for improvement.
“Flickering” between refresh rates
Since the Pixel 4s’ panels do not have a true variable refresh rate, Google uses separate display modes with different display timings for 60Hz and 90Hz (which is normal for any non-variable refresh rate display). This results in different display characteristics for the two modes, and individual calibration tables are necessary for both modes to appear similar. However, a perfect calibration is pretty much unattainable at mass production. For OLEDs, calibration missteps and signal drift/variance are very noticeable for dark shades at low signal levels, similar to increased camera noise in low light. In the Google Pixel 4 and Pixel 4 XL, the differences in calibration of the two refresh rates are evident in their darker shades. For both phones, the 90Hz display mode is tinted more green-cyan than in its 60Hz display mode. The difference is most noticeable at low brightness for dark colors, being the most severe between 10-20 nits. This variance is the reason for Google’s difficulties with implementing their auto-switching Smooth Display system. Note that Google is not the only OEM with this issue; differences in calibration are also present between the different refresh rate modes in other high refresh rate OLED panels, like OnePlus’ latest phones, or the ROG Phone II.
Pixel 4 Color Accuracy
Average sRGB color accuracy plots for Google Pixel 4, Natural profile
Comparative color accuracy chart
One area where Google has usually excelled in is color accuracy. Their phones have been competitive in color accuracy every year, and Google manages to continue this trend in 2019. Our testbench for color accuracy consists of 37 constant-luminance points at five different stimulus levels, over the display’s brightness range. Most colors in images and films are within 15–40% intensity, while colors in app/web design & UI commonly consist of tones above 50% intensity, so it is important to measure colors at all stimulus levels. The new ΔETP color difference metric improves on these lower-stimulus readings, which we now use to assess the total color accuracy of a display.
Accurate white point?
Both our Google Pixel 4 and Pixel 4 XL units have white points that are remarkably accurate to the D65 standard. Our Google Pixel 4 average white points measure at 6586 K (ΔETP = 1.3), while our Pixel 4 XL measures more accurately at 6477 K (ΔETP = 0.4). Although I would like to rave about how accurate these white points are, Google is internally targeting a white point of D67 (6700 K), so I can’t say that they hit their mark. However, I’d like to note that a D67 white point for OLEDs may actually be more accurate than targeting D65, since modern OLEDs are subject to metameric failure (due to narrow spectral band primaries from wide color expansion), and appear warmer than an LCD or a CRT at the same spectral power distribution.1 2 Because of this, I actually wish more OEMs would target this white point for OLED displays. Also, most of them tend to ship with white points warmer than their target, anyway.
Improved color lightness
Some previous Pixel devices, while being accurate chromatically, exhibited contrast issues and darker colors than standard. This was a common issue with all OLED panels up until the Samsung Galaxy S9, which was the first smartphone display to control its brightness-APL response. Google fixed this on the Pixel 3 XL, but the LG panel on the Pixel 3 still had the issue. With the new LG panel on the Pixel 4, Google has also improved its brightness-APL response, and now both the Pixel 4 and Pixel 4 XL have excellent total color accuracy. Both displays have an average ΔETP lower than 3.0 for sRGB and Display P3, with small maximum errors. However, when considering luminance error, we see that the smaller Google Pixel 4 does seem to have additional issues in color lightness beyond gamma. Although the contrast on the smaller Google Pixel 4 is quite accurate, some colors still appear slightly darker than expected, particularly within the red color mixtures and blues. This could be caused by its white point creeping towards magenta, away from green which makes up most of the luminance in RGB color mixtures. It is still a clear improvement over the Pixel 3, and these lightness issues should not be noticed by most since it is below our reference threshold (ΔEI = -2.8)
Industry-leading color accuracy
On the Samsung display in the Pixel 4 XL, Google is showing industry-leading total accuracy, exhibiting the lowest color errors I’ve seen on any of the latest smartphones in our thorough testbench. The Pixel 4 XL measures an average total color accuracy ΔEITP of 1.7, which is a noticeable leap ahead of other 2019 flagships. For maximum intensity colors, the Pixel 4 XL shows color accuracy performance that rivals and even outperforms many professional reference monitors, with an average ΔETP of 0.9, which is under our visual threshold (ΔETP < 1).
While the displays on the iPhone 11 Pro and the Galaxy Note10 are still currently best-in-class, they share two flaws: both have warmer white points than standard, and both exhibit oversaturation at lower intensities [iPhone 11 Pro, Galaxy Note10]. Most display reviews don’t cover lower-stimulus colors (DisplayMate only tests max-brightness & max-intensity test colors), and most display reviews use the older ΔE2000 color error metric, which under-reports lower-intensity colors because the metric assumes visual adaptation to a specific white level. Thus, the older ΔE2000 metric is not as effective for content with lower picture levels (most films; colors in dark mode apps) or for HDR color accuracy assessment. The Google Pixel 4 and Pixel 4 XL do show slight undersaturation at lower color intensities, but overall maintain great accuracy at all intensities.
Pixel 4 Contrast & Tone Response
Average gamma for the Google Pixel 4
Display contrast and gamma tend to be regarded as the most important factors in an accurate display. Since Google sources their displays from two different vendors, there’s bound to be differences between them. The most important differences are usually found within their gamma scales, and the gamma behavior between the Google Pixel 4 and Pixel 4 XL panels are actually quite different.
Unstable Pixel 4 XL gamma
The Pixel 4 XL’s gamma calibration is a little troubling. At maximum brightness, the Google Pixel 4 XL display contrast is pretty much perfect — it’s a completely straight 2.20 gamma power. However, as display brightness reduces, the Pixel 4 XL’s gamma changes. Around 50% brightness (~200 nits), the Pixel 4 XL’s gamma scale is no longer straight and sees a steep decline in dark shades. At about 70 nits, the Pixel 4 XL seemingly takes on a different display calibration with a jagged gamma that approximates a high 2.43 gamma power. Colors below 10% intensity, which covers a large portion of the shadows in images, are so dark that they are pretty much clipped. At medium-to-low display brightness, the contrast in the Pixel 4 XL is a slight regression from the Pixel 3 XL, except that Google has fixed the gross miscalibration present in the Pixel 3 XL at minimum brightness. I can’t help but think that Google has focused primarily on making the max brightness gamma accurate to gain a high mark from DisplayMate, whose testbench only measures gamma at max brightness. Not only in gamma, but in color accuracy as well. This is similar to the Galaxy S10 and Galaxy Note10 (Snapdragon) where only max brightness has a straight 2.20 gamma power, and it gets progressively worse at lower display brightness.
Normal (left), bugged gamma (right)
There also seems to be a bug exclusive to the Google Pixel 4 XL which results in jarring display calibration. From my testing, the Pixel 4 XL applies the wrong gamma calibration when waking the display up with 90Hz enabled and Always-On Display disabled. Both the 90Hz and the AOD modes have their own display calibrations, and the Pixel 4 XL gets confused somewhere in figuring out what display calibration to apply when waking up the display. The bug isn’t too noticeable above 50% brightness, but it does still slightly affect the white point and display saturation. The issue becomes increasingly severe at lower brightness, shooting the display gamma through the roof at minimum brightness and substantially clipping color tones.
Pixel 4: Most improved (LG) display
On the other hand, the smaller Google Pixel 4 has fantastically calibrated display contrast, which can be partially accredited to its fixed brightness response to APL. It has an impressively low variance for its upper display brightness range, ranging just between a 2.21 and a 2.23 straight gamma power. For lower brightness levels, the Google Pixel 4 lifts its shadows, which results in a lower display gamma. This is both a blessing and a curse, as the Google Pixel 4 shows exemplary OLED near-black rendering at the cost of reduced image contrast at lower display brightness. The Google Pixel 4 is the first Android OLED display I have seen to be capable of rendering its first 8-bit depth intensity (1/255, #010101), and its near-black rendering capabilities remain excellent down to its minimum brightness where it can still render 2.4%-intensity (6/255) gray. Only the iPhones have been capable of doing this on a mobile OLED, up until now. The iPhone OLEDs, too, lift shadows at the dim end for better near-black rendering; it’s currently a necessary trade-off to keep image fidelity viable in dark viewing conditions. However, at minimum brightness, the Apple iPhones and the OnePlus 7 Pro are still superior in black clipping than the Google Pixel 4.
This is a surprising development since the LG panel in the Pixel 2 XL was notorious for abnormally-high black clipping. The Pixel 3 also had an LG panel, and it showed improvements in black clipping, but it was still noticeably higher than that of typical Samsung panels. I only expected a marginal improvement with the LG panel on the Pixel 4, but I’m actually quite shocked by how much the LG panel improved this time around.
Pixel 4 HDR10 Playback
While HDR content on smartphones is typically still limited to just Netflix and some short films on YouTube, it’s always fun to see the bleeding-edge capabilities of our little pocket computers. Supporting good HDR10 accuracy now could add a nice layer of future-proofing for the eventual proliferation of HDR content — though whether it’s the HDR10 standard that’ll be dominant is yet to be seen. I only managed to have time to test HDR10 in the Google Pixel 4 XL (and only 8-bit intervals), and it does just okay.
At a peak brightness of 600 nits, the Google Pixel 4 XL does meet the HDR standard brightness of at least 540 nits for OLEDs. But compared to the 1200+ nits claimed on the Galaxy Note10 and the iPhone 11 Pro, the highlights on the Pixel 4 XL seem dim. Furthermore, the Google Pixel 4 XL seems to remarkably undertrack the lower 15% of its signal range, rendering those critical dark scenes much darker than intended. It does provide a smooth roll-off into its peak brightness though, instead of just clipping.
Moving forward, the excellence of the Google Pixel 4 XL’s color accuracy extends on to its HDR Rec. 709 accuracy. Although it is not reference-level, a ΔETP of 3.4 is still very good. However, most HDR10 content extends up to DCI-P3, which is much more demanding to accurately reproduce. The standard for HDR DCI-P3 is typically a nominal white level of 1000 nits, and the Pixel 4 XL is not even capable of getting that bright. So as expected, the Pixel 4 XL cannot cover a good chunk of the HDR DCI-P3 gamut, and it breaks down at reproducing the higher inner color mixtures (orange, pink, and purple).
Final Thoughts
This year, Google closed the gap between the two displays more than ever before. Their calibrations match up much more evenly, but now they both have individual characteristics that prevent one display from being the clear superior. Although the Pixel 4 XL may have colors that measure more accurately, I’m hard-pressed to see the difference at these scales. Furthermore, I believe that contrast is the most important factor in an accurate image, and the Pixel 4 consistently performs better than the Pixel 4 XL throughout its brightness range. The Pixel 4 also has excellent shadow rendering that rivals the iPhones’, and I’m a consumer of a lot of content where this matters. However, the grayscale inconsistencies are noticeable and annoying, and it puts me off the Pixel 4 seeing different gray UI elements with different tints. Luckily, my Pixel 4 had excellent display uniformity for dark gray, but I’ve already seen many posts regarding regional screen tints. And this leads into the display lottery, which I’m certain will still be a big issue for the LG panel on the Pixel 4 this year.
Consumers paying $800+ should not be worrying about something like a dim display or a lottery in 2019, but that seems to be a recurring theme for Pixel devices
And as expected, my biggest gripe with both displays is their poor brightness. I live in California — a bright display is an absolute must during the summer. I also typically keep my phone on a car mount while I’m driving, and I’ve found all Pixel phones to be pretty poor for this because of their brightness. A bright screen is just an overall much better experience outdoors, and there’s no use for the best calibration in the world if you have difficulties seeing it in the first place. It would also improve the camera experience, which seems to be Google’s main selling point. Sure, its brightness may not be an issue for others depending on what they expect from their phone, but that doesn’t invalidate the issue for the many that see it as such.
“It’s better to have and not need, than to need and not have.”
OnePlus, a company much smaller than Google, was able to secure next-gen panels from Samsung that gets just as bright as the Galaxy Note10 and the iPhone 11 Pro, and they released the OnePlus 7T at about the same time as the Pixel 4. The iPhone 11 Pro, which is the phone that Google is trying to directly compete with, was released earlier than the Pixel 4 with Samsung’s latest panels. Google should have definitely been able to do the same had they actually made an honest effort in using the best parts that they can. It feels as if Google really prides itself on finding workarounds for hardware “bottlenecks,” but sometimes it just seems like it’s to a fault — and in those cases, they should just use better hardware.
Google Pixel 4 Forums ||| Google Pixel 4 XL Forums
Buy the Google Pixel 4 or Pixel 4 XL
| Specification | Google Pixel 4 XL, Natural | Google Pixel 4 XL, Adaptive |
|---|---|---|
| Brightness |
Minimum:
1.9 nits Peak 100% APL:
437 nits Peak 50% APL:
434 nits Peak 1% APL:
430 nits Peak HDR 20% APL:
596 nits |
|
| Gamma Standard is a straight gamma of 2.20 |
2.20–2.43
Average 2.28 90Hz:
2.22–2.28
Average 2.25 Varying gamma
Can be slightly high |
|
| White Point Standard is 6504 K |
6477 K
ΔETP = 0.4 |
|
| Color DifferenceΔETP values above 10 are apparent ΔETP values below 3.0 appear accurate ΔETP values below 1.0 are indistinguishable from perfect |
sRGB:
Average ΔETP = 1.5 ± 1.2 Maximum ΔETP = 6.4 Outstandingly accurate P3:
Average ΔE = 2.0 ± 1.6 Maximum ΔETP = 8.8 Outstandingly accurate |
22.6% larger gamut than Natural profile
+11% red saturation, slightly shifted orange (ΔETP⊥ = 7.0)
+19% green saturation, slightly shifted mint (ΔETP⊥ = 3.4)
Identical blue saturation
|
The post Google Pixel 4 & 4 XL Display Analysis appeared first on xda-developers.
from xda-developers https://ift.tt/2QorIs0
via IFTTT
Aucun commentaire:
Enregistrer un commentaire