As the price of ultra-premium smartphones continues to rise, what are companies doing to distinguish their displays from the rest? Are there still areas that they can improve on without needing to adapt new display hardware?
These are questions that become more uncertain as the quality of display panels inevitably increases across the entire price spectrum. In an effort to address the first question, OnePlus includes a collection of somewhat unique features in its flagship OnePlus 9 Pro device, such as video motion interpolation, automatic display white balance, and SDR-to-HDR video conversion. Although my two opening questions are directly related, I maintain that the best way to satisfy the first question is by focusing on the second question—new hardware naturally comes to every company, but not every company makes good use of new hardware. How does the OnePlus 9 Pro fare?
OnePlus 9 Pro Display Specifications
OnePlus continues to source high-end OLEDs from Samsung Display for its flagship. The OnePlus 9 Pro bestows a large, super-sharp 6.7-inch front panel with 525 pixels per inch, and it supports a 120 Hz refresh rate for smoother motion and interaction with the phone. It is very similar in specs to last year’s flagship model, but the OnePlus 9 Pro is in fact using updated display internals.
A new set of luminescent materials with enhanced emissive efficacy is being used for the OLED, and a new display backplane technology called LTPO is incorporated to further improve the power efficiency of the display. And finally, the display driver IC of the OnePlus 9 Pro now natively supports 10-bit color depth instead of resorting to 8-bit + 2-bit FRC. If these specs seem familiar, it’s because the panel that OnePlus uses is actually identical to what OPPO uses in the Find X3 Pro.
The new hybrid backplane utilizes IGZO driving transistors which require less power than conventional LTPS transistors to output the same amount of light. In addition, IGZO transistors have significantly lower off-leakage current than LTPS transistors, which makes them more suitable for driving display panels at lower refresh rates since they can hold their charge sufficiently. The oxide transistor is the catalyst for a viable true hardware-level variable refresh rate, and it means that the OnePlus 9 Pro’s high refresh rate panel should be much less battery-taxing than its predecessor.
All of Samsung Display’s smartphone OLED panels utilize a PenTile diamond subpixel arrangement, including the one on the OnePlus 9 Pro. I thought it would be interesting to compare OnePlus’ subpixel layout to a couple of other flagship OLEDs, and by doing so, we can see clear differences in subpixel proportions; the iPhone 12 Pro Max’s OLED panel has relatively much larger subpixels than both the OLED panels in the OnePlus 9 Pro and the Samsung Galaxy Note20 Ultra, especially with respect to blue subpixels.
It’s been purported that the OLEDs in iPhones have greater pixel fill factors (the proportion of the total pixel area that is actually emissive, also known as aperture ratio), and we now have verification of this. Using microscope photos (taken by the OPPO Find X3 Pro) as reference, I’ve coarsely calculated the iPhone 12 Pro Max to have a fill factor of approximately 35-40%, while a typical Samsung Display OLED measures only about 25–30%.
The main advantage of a higher pixel fill factor is greater pixel longevity. Larger subpixels will last longer (assuming luminance is normalized), resulting in slower display burn-in. Another thing to note is that blue emitters in OLEDs have by far the shortest lifespan, so they degrade the fastest. This is why OLEDs typically tint towards yellow over time as the red/green/blue OLED emitters decay at different rates. In our subpixel comparison, the iPhone 12 Pro Max contains blue subpixels that are relatively about 70% larger than those of OnePlus’, and as a result, the OLED panel of the iPhone 12 Pro Max should experience burn in more slowly and exhibit less yellowing over time than a typical Samsung Display OLED.
OnePlus 9 Pro Display Features
Included in the OnePlus 9 Pro are several display features that can adjust the screen or the media content that is being played.
Motion Graphics Smoothing increases the smoothness of video content (in supported apps) by interpolating additional frames, converting video up to 60 frames per second (or 120 FPS when enabling it in the OnePlus Laboratory). This sort of feature is found in many TV sets, and while it can make motion appear smoother and clearer, some people dislike it since it can make content look like soap operas, or other times it can just look wrong. It also has the potential to render unwanted artifacts within the generated frames. From my usage of this feature on the OnePlus 9 Pro, the motion interpolation works very well in smoothing motion without significant artifacts, although the smaller screen estate of a smartphone display may just mean that artifacts are less perceptible.
Comfort tone is functionally identical to Apple’s True Tone. It adapts the white balance of the display to better match that of your viewing environment, which can help improve the consistency of the appearance of white. The adjustment range for the color temperature of white varies from 5000 K to 7400 K, and from my usage, the feature tends to shy away from tinting too warmly relative to the environment when compared to True Tone. During transitions, the shift is very seamless, so you may not be able to even perceive that the feature is doing anything at all. This means that the feature is working well. There is a controversy behind this type of feature due to the belief that it impacts color accuracy, but in actuality, the perceived colors on a screen are changing all the time whenever the surrounding light changes; features like auto brightness and auto white balance attempt to counteract some of the perceptual shifts that occur whenever the viewing environment changes. The potential utility in these features depends on if the feature itself works seamlessly, and I do think that Comfort tone works pretty well.
Hyper Touch is a setting exclusive to the OnePlus 9 Pro that increases the touch polling frequency up from 240 Hz to 360 Hz. Enabling this feature should improve touch latency, however, I was unsuccessful in detecting any difference no matter the game/application since the response time with the feature disabled is already very good. OnePlus notes that it may cause minor flicker in some scenes, but I haven’t seen that happen. Out of curiosity, I briefly tested to see if the feature improved the pixel response time for dark pixels, but alas, the same amount of ghosting/”purple smear” was present.
Vibrant Color Effect Pro increases the contrast and saturation of video content, intending to upscale the content from standard dynamic range to high dynamic range. At the time of writing, this feature seems to be ineffective since I have not been able to get it to work at all despite toggling a dozen combinations of the display settings.
Ultra-high Video Resolution is an AI upscaling feature that increases the sharpness of video content in supported apps. So far, there appear to only be three apps that are supported: WeChat, Instagram, and Snapchat.
Vision Comfort is OnePlus’ version of Night Light, which reduces the emission of blue light by making the screen warmer. However, this feature is slightly different since it can also lower the saturation of the display to make it more comfortable to look at in low light.
OnePlus collaborated with Pixelworks, a company that specializes in video and image processing, for some of these features. Inside the OnePlus 9 Pro is Pixelworks’ X5 Pro visual processor which handles the HDR upscaling (Vibrant Color Effect Pro) and the motion processing (Motion Graphics Smoothing). Two MIPI lanes feed the Pixelworks chip, which are used to send over the video stream and the Android UI surface over separate lanes. The X5 Pro processes the video stream independently and then sends a composited frame with the UI to the display. We have published a separate article that covers what else the Pixelworks chip can do. Pixelworks is also responsible for the factory color calibration of the OnePlus 9 Pro display. Some notable features that existed on the OnePlus 8 Pro seem to be missing in this year’s model, however, such as DC dimming and the Night mode Lightness slider.
Source : https://www.xda-developers.com
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