Optimizing mobile display brightness by leveraging human visual perception

Modern smartphones and tablets are battery-constrained by their mobility; this constraint is heavily factored into any design decision made on the device. Furthermore, the display is one of the most power-consuming subsystems. Adaptive display brightness systems attempt to address this high display power consumption by setting the brightness depending on the surrounding ambient light levels. In this work, we run a series of user studies aimed at gauging the accuracy of these adaptive brightness models. These studies compare subjective satisfaction and readability metrics on a common smartphone display and find that the adaptive brightness system isn't well-tuned to user preferences. We also find that subjective ratings and readability are closely correlated with one another across different display brightness levels, which can be used to give a better understanding of how screen brightness levels impact users. Additionally, we note that operating systems need to reduce the power envelope of the device for a variety of reasons. This is done without understanding the impact of these decisions on user satisfaction, and can significantly degrade user experience. In this work, we propose a user-aware method of reducing display power consumption, which allows display power to be throttled while understanding the resulting impact on the user. By considering this impact on the user, we devise an optimal dimming scheme which can reduce the time-weighted readability degradation by upwards of 21.5%.