Appropriate Screen Brightness for Ambient Lighting Illuminance

The popularization of display technology resulted in significant conveniences yet several drawbacks meanwhile. Threats to visual health caused by displaying screen were generally from mismatch between screen brightness and ambient lighting illuminance. Recent researchers on smartphones developed various methods to automatically modulate the screen brightness dependent on ambient lighting illuminance, whereas the modulated screen brightness values were perceived to be lower than needed. In this study, we compared the effects among various smartphone-brightness values on ocular physiological parameters in different ambient lighting illuminance values. We found that the automatically-modulated brightness of smartphones were improper for human eyes due to the lack of enough photons to activate necessary ocular contrast, and the brightness values should be increased by 10-20% to protect ocular function and keep visual health.