FP2: Adaptive Brightness: Problems & it's Logic


I would like to use adaptive brightness for battery saving but regardless of the environment the display keeps being even less bright than setting brightness to 10%.
With this it is impossible to see anything on the display when for example outside on a cloudy day (not even talking about direct sunlight).

Is anyone else seeing this issue or is it just me?
Am I missing a configuration option here?

Thanks for feedback on this…


but you can manually increase brightness to any value?

Yes, of course, manually changing is possible - this just lacks the wanted battery saving effect and means manual action each time a change is necessary.
Seems a bit odd to adjust brightness each time you unlock your smartphone in a differently lighted environment than before, right?

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I’ve noticed similar behaviour

Me to. I have the feeling it just doesn’t adjust at all. It stays at the value I set.

Though I don’t think it’s a software bug. For me the display setting “adaptive brightness” works fine, it’s just a little bit slower reacting than on other phones I had, but I have no problems with it.

Is it possible you have some dirt/dust in front of the light sensor?

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Interesting question … where exactly is the light sensor on the phone?

BTW: I might be missing it but is there some picture denoting all the visible parts of the phone at front and back (at least it is not in the short manual that comes with the phone)

Actually Freibadschwimmer is right. It is just pretty slow but after a couple of seconds it does adjust.

Not exactly. but have a look at the iFixit-Teardown-Guide:

Here you see the front of the FP, maybe we should make a better labeling in the forum…:

If the light is not measured through the camera, it should be measured at the unit of the proximity sensor wich I labeled red. But I could be wrong…

Cheers, Robert

I experienced the slow adaption to changing brightness of the environment too. It takes about 5 seconds to adjust, which is quite a while but with my old phone (S3) it also took a couple seconds.

I’ve also noticed that it’s not a smooth but rather juddery adoption.

I think therob was right with the location of the light sensor. When i put my finger over it, the display dimms.

So that means, the sensor is in the top left corner, between the notification led and the speaker.

OK, I could confirm that it also works with my FP2.

Making extreme changes, i.e. putting it right under a light source, significantly increased brightness, putting it away from that light source decreased brightness after some delay time.
So far so good - nevertheless to me it feels too dim, especially outdoors but also indoors - e.g. at the moment (at night in a fairly lit room) putting the display brightness to 10% is significantly brighter than adaptive brightness.

So I think that the mapping of sensor detected environment conditions to display brightness could be improved - and this IS probably a software issue.

I think that the adaptive brightness setting works on top of the manually set brightness.
With the adaptive br. on, I just tried to set manually the brightness, and despite having the adaptive on, it makes a difference to what the brightness is set.

I have the brightness setting in the middle (appr. 50%) and the adaptive brightness turned on. I cannot complain, for me the brightness works fine (besides the known flickering bug).

Already since 2 months I am wondering about the logic of the “Adaptive Brightness” (=“Auto”) feature of the FP2 (or is it stock Android stuff?)…

As @freibadschwimmer already assumed, Auto is set on-top of the manual settings.
But until now, I could not find a good setting which sweets all situation I have (dark inside, bright outside).

My tests: “Auto” is enabled…:

  • If I set the manual value to the lowest value, the brightness does NOT increase in bright conditions at all (or I can’t notice it in the sun, thu I cant see anything outside).
  • If I set it to the max: it is at max (and eats battery like hell)!
  • If I set it to a middle value: It is far to bright inside, but reacts good in the sun and I can see something
  • If I set it to a very low value in the dark, to see enough but to save battery in the dark, in the sun it never becomes bright enough to seeing enough.

So, I am puzzled how to use this “feature”…
Can anybody help out and already undestood how it is/should working?

And I am afraid to try adjusting the “auto” values with gravity box (where for each light-sensor-value a brightness-value can be set between 0 and 255).

Comparison with FP1 - there it is that simple:

  • Set it manually to low/mid/bright
  • Use the Auto feature (which can be tuned with gravitybox for shifting it to a even lower or brighter level, or shift only the min/max of the auto-range)

So, again I am very surprised about this SMARTphone Auto-feature of FP/Google…


I also have this problem. I have my brightness level right in the middle. I find in low light sometimes it “adapts” and goes far too low. It might then recover but it’s very hit and miss.

Has nobody an idea about my question, how the auto/adaptive-brightness do work and how it should work?

I still cannot see any logic in its behaviour (see above)…

This post from Android Police explains how the adaptive brightness works:

In contrast to the auto brightness in older Android versions, the display does not change its brightness in the full spectrum (from 0 - 100 %) anymore, but only in a range around the selected brightness value. This should allow the user to set a base value, which yields the most comfortable display brightness in different situations. Unfortunately it seems that the developers forgot that users might not only want to set a bias, but also the range for the brightness adaption, because they fixed the brightness variation range to a fixed value.

How this works can be observed when the device is in a dark surrounding. If the brightness thumb now gets dragged from low to high, there is a rather long interval, where nothing happens. This is because the algorithm, which sets the display brightness, wants to set it to the minimum value. As long as the slider thumb is no more than the fixed brightness variation range away from the 0% mark, this means that the minimum value is 0%.

As soon as the slider thumb is further than the fixed brightness variation range away from the 0% mark, the display brightness increases, because the lowest allowed value for the algorithm is now at the lower border of the brightness variation range. Because this border is moving together with the slider thumb (unfortunately not visibly), the brightness increases.

This means that setting the slider thumb to either the minimum or maximum value yields a loss of brightness adaption of 50%. To have the maximum adaptation, make sure that the slider further than the adaption range away from 0% or 100% brightness.

In a quick test, I observed that the brightness begins to increase at a value of about 50% in a dark surrounding. This would indicate that the brightness variation range is about 50% around the selected slider value. Thus the middle position of the slider should yield the best adaption range. If you want to get rid of the display flickering, set the slider a bit above 50%. Then the brightness never gets into the critical area.