Comment 3 for bug 1632469

I played around a little more with this problem. When the screen comes on after 50 seconds, it returns to the dimmed level -- not to the fully brightened state. This happens when the phone is set to lock screen after one minute of idleness.

If the lock screen timeout is set to 30 seconds, the dimmed display appears 20 seconds after pressing the power button. If the timeout is 2 minutes, then the phone display appears dimmed after 1:50.

In each case, the screen comes on in dimmed mode in ("Lock screen after" time - 10) seconds. Since under normal conditions the display dims about 10 seconds before locking after a period of non-use, it suggests that the phone thinks the display is active on pressing the power button, and is dimming it to alert the user that the device is about to lock itself.

Hope this provides some useful info.