I believe they changed the way auto-brightness works for the iPhone 4S (and up) in iOS 6. The old method would be that the auto-brightness would only kick in when the screen unlocked and the brightness bar would never move. The new method is that the phone is constantly updating the auto-brightness (which seems like it would drain the battery to me) and the bar moves. They also seemed to change the way auto-brightness is calibrated.
Try the following which seems to have worked for me:
1. Turn on auto-brightness
2. Take you phone someplace very dark and unlock it and then go and manually set the brightness to your preference.
3. Lock the screen.
4. Go someplace very bright (put the phone underneath a lamp or something) and unlock it and then go and manually set the brightness to your preference.
This should do it. Basically you are setting your minimum and maximum brightness. The phone should now never go below the minimum or above the maximum.
Note, this seems to only be for the iPhone 4S (maybe the iPhone 5). My iPad 2 still works the old way.
Also, try this if you want custom brightness settings automatically adjusted for each environment...
Refer to Figure 1 in http://www.displaymate.com/AutoBrightness_Controls_2.htm
Prior to iOS 6, the control function of Auto Brightness is pre-determined based on the Brightness slider value you set. Figure 1 shows 4 such curves; 1/4, 1/2, 3/4 and Max.
In iOS 6, http://www.reddit.com/r/apple/comments/10a9p0/til_how_the_ios_6_auto_brightness_ works/ propose that users can dictate their own brightness function.
- In ambient brightness of value a1, if you're not happy with the proposed brightness by the phone, you set it to some brightness level, say b1.
- In ambient brightness of value a2, if you're not happy with the proposed brightness by the phone, you set it to some brightness level, say b2.
- In ambient brightness of value a3, if you're not happy with the proposed brightness by the phone, you set it to some brightness level, say b3.
From now on, each time the phone goes into ambient lighting of level a2, it will automatically go into brightness level b2.
Your second link was the solution I was looking for. It also gives an understanding of how auto-brightness works in iOS 6.
From what I gather, there are two options for using auto-brightness: The first lets the iPhone adjust to its pre-programmed default screen brightness levels based on differently lit environments. The second "trains" your iPhone's auto-brightness mechanism to auto-adjust its screen brightness to your custom desired levels of brightness in differently lit environments.
- Totally Automatic Setting: Turn auto-brightness to OFF. Go in a dark room. Move the slider as far left as you are comfortable with in that dark environment. Turn auto-brightness to ON. Done. Now, move to a brightly lit room and watch the slider adjust to make the screen brighter. Go to a differently lit room, and watch the screen brightness adjust to that environment. Keep a note of whether you like these particular screen brightness settings. If you would prefer a little brighter in one room and a little darker in another from the automatic settings, then you will want to use option 2: Custom automatic setting.
- Custom Automatic Setting: Turn auto-brightness to OFF. Go in a dark room. Move the slider as far left as you are comfortable with in that dark environment. Turn auto-brightness to ON. Done? Not quite. Here is where you make your custom adjustments.
* Move into a brightly lit room. Watch how the slider adjusts to make the screen bright. Wait until it stops adjusting. Now, if you think it should be brighter or less bright in that environment, move the slider to the brightness setting you prefer. Do NOT turn off the auto-brightness setting. This is how you make your custom adjustments.
* Now, move to a differently lit environment, like a darkened bedroom. Let your iPhone adjust its brightness to that environment. When it stops adjusting, is the screen brightness at the setting you would like? If so, then do nothing. If not, move the slider accordingly. Again, do not turn off the auto-brightness setting.
* Continue doing this for other differently lit environments.
Let us know if it works for you all.