One of the most appealing features of Google Pixel 4 – The 90Hz mode – has a flaw. Currently, the high-quality screen frequency drops to a standardized 60Hz when the brightness is below 75%. Google promised to fix it, or at least, bring the mode to more “brightness conditions”. But still, the search giant has failed to explain why it will be necessary. We know that 90Hz consumes more energy than standard 60Hz, and Pixel 4 has a mediocre battery capacity. However, if 90Hz is available why to limit its usability?
The folks at XDA-Developers found a reason after digging in the code commit comments. According to the investigation, the display uses different calibration profiles for 60Hz and 90Hz modes. Apparently, the display manufacturer hasn’t matched them perfectly. As a result, the smartphone operates with slightly different display levels. It’s not so aggressive, but the downgrade is easily noticeable by users. After all the display is switching between the 90Hz and 60Hz fairly often.
“Due to hardware limitation, flickers are seen when switching between 60 and 90hz at low display and ambient brightness. Force the display to stay at 60hz when ambient and display brightness are low. The display uses different gamma curves for different refresh rates.
It’s hard for panel vendor to tune the curves to have exact same brightness for different refresh rate. So flicker could be observed at switch time. The issue is worse at the gamma lower end. In addition, human eyes are more sensitive to the flicker at darker environment. To prevent flicker, we only support higher refresh rates if the display brightness is above a threshold. And the darker environment could have higher threshold.”
The difference in the calibration is more pronounced when the brightness is set at lower levels. In addition, our eyes become more sensitive to changes in brightness in the dark. The screen flickering issue is easily fixable when you force your screen to always work on 90Hz via Google Pixel 4 Developer Settings. Still, it lifts some questions. Will Google implement changes in the brightness or the company will improve the profiles for both refresh rates?