# Automatic display brightness calibration?



## danisawesome (Oct 3, 2011)

So, just installed 2.1 and switched on the auto brightness only to find that it behaves a little erratically. It is constantly hunting, brightening the display, then dimming and repeating. It usually will settle down for a minute, but will start up again soon after. Is there some sort of calibration I can perform to get it to settle down? Or maybe just a general overview of how the settings function? The Cyanogen wiki is a little sparse on details for this setting.

Thanks!


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## Phryxus (Oct 18, 2011)

So are you asking for explanations of the settings under the CM Settings-> Display-> Automatic Backlight menu? I'll give a short explanation on them:

-Light sensor filter: basically means the device will not react to instantaneous values from the light sensor on the device. It averages values over a period to prevent the display from changing often ("constantly hunting, brightening the display, then dimming and repeating" as you put it). The settings inside set the length of the period to use as an average (longer means individual values will have less of an impact), a minimum lux change to reset the counter (ie if you gets really bright all of a sudden from say walking outside, it will allow it to react quickly and "reset' the window), and how often to take a reading from the sensor (more often = faster reaction, but more CPU drain)

-Use custom under light levels lets you set a different minimum brightness to the screen (in a 0-255 range). 0 would be backlight is off, 255 backlight at full. Experiment if you want it darker when you are in a dark room for instance.

-Allow light decrease to my understanding means that when the sensor reports a value X% (whatever you set) BELOW the backlight range it is currently in, it will not decrease the backlight. So say your reading is at 120 (in a range of 100-500), hysteresis is at 20%, then the device will NOT change the backlight until the reading drops below 80. When increasing, it will behave normally.

I'm not aware of any calibration you can run, per say, but you can tweak all of the values to get something that works better for you. I haven't messed with it on my TP yet, but with CM7 on my Droic Inc, I can't get it perfect simply due to the light sensor itself. If you go under "Edit other levels..." you can see the current sensor output for reference in editing your backlight levels.

This link has an explanation of it on the DInc, which should be similar in theory to any CM7 device. To keep in mind, it won't be perfect because "the light sensor can only detect a fixed number of raw values."
http://forum.xda-developers.com/showthread.php?t=1003592

Hope that helped out some!


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## danisawesome (Oct 3, 2011)

Thank you for the information on the settings and the sensor itself! That will definitely help me get things tweaked to where I get the results I want. I wasn't sure if there was a rough guide or guidelines to calibrating the light sensor to work properly, but this will help immensely. Maybe I'll end up finding a good, streamlined way of adjusting things and make a short how-to about it, assuming one doesn't exist somewhere already.


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## CiscoStud (Oct 2, 2011)

I use beautiful Widgets to control my brightness. I just select the Widgets to adjust. Feels good and saves my juice.

Sent from my HP Touchpad using Tapatalk


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