Ever since I upgraded to A9 I can’t take the brightness of th screen as low as before. It seems there’s this file
/sys/devices/mdp.0/qcom,mdss_fb_primary.171/leds/lcd-backlight/brightness that controls the minimum value (or is it a multiplier?) that one can set. Of course, you can’t change the contents of that value unless you’re root. For more details, see here:
Can someone prod the developers and ask them to change this value to what Android7 had?