there is a similar question to this one How does the automatic brightness settings work?

however, I do not think it answers my question. This is more to do with the UI.

I just got myself a Galaxy s3. The phone has under the notifications the ability to change the brightness. print screen

As can be seen from the screenshot, I can both adjust the brightness manually and select auto. Adjusting the brightness manually does visually affect the brightness of the screen even when the autobrightness is checked.

So what does the manual adjuster do when auto-brightness is turned on?

  • This looks misleading, if 'Auto' is checked, the slider should be disabled, likewise, if 'Auto' is un-checked, the slider should be enabled. Or, more than likely, the slider overrides Auto, thereby leaving you with the choice! :)
    – t0mm13b
    Commented Jan 30, 2013 at 3:31
  • That seems weird. In S2, the slider is disabled on Autobrightness. I would flag that as a bug.
    – geffchang
    Commented Jan 30, 2013 at 4:13
  • @t0mm13b - If it overrides the auto choice, shouldn't it also uncheck the auto feature as well? I just checked, it's also in the settings, so it's definitely not a bug in the widget. The other weird thing is the brightness adjusts much greater when auto is off, then when auto is on.
    – Diskdrive
    Commented Jan 30, 2013 at 4:42
  • If auto is checked, and the slider still enabled, I'd expect the slider value as a kind of "base value" for auto adjustment. But your last comment is really confusing -- as it suggests auto is on when auto is off...
    – Izzy
    Commented Jan 30, 2013 at 7:04

1 Answer 1


The Auto option enables the lightsensor of the device.
On some Samsung devices there remains a slider when the checkbox Auto is checked.
With that slider you can set a delta (small change) in the brightness set by the data of the sensor. You can chose if you want it a bit brighter or less bright than the sensors standard value.

In short:
- Box checked: Sensor defines brightness (+/- delta)
- Silider in the middle: delta = 0
- Slider to the left: delta = - amount of steps from the middle
- Slider to the right: delta = + amount of steps from the middle

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