How to enable auto brightness in macbook pro os x lion

[Mollyi7]

I am using a Macbook Pro which is running on Mac OS X Mountain Lion 10.8.3. Whenever I put this laptop on sleep mode and after sometime I open the lid then then display will be too black like brightness is reduced to 5% or so? Is there some kind of bug in this laptop or is it happening in my macbook only? If there is a solution to this problem then please let me know about it. Thanks

[Asclepius]

Try to reset the SMC on Mac portables with a battery you can remove:

1. Shut down the computer.
2. Disconnect the MagSafe power adapter from the computer, if it's connected.
3. Remove the battery.
4. Press and hold the power button for 5 seconds.
5. Release the power button.
6. Reconnect the battery and MagSafe power adapter.
7. Press the power button to turn on the computer.

More methods are given on this link - http://support.apple.com/kb/HT3964

[Erinyes]

I am using a dual monitor with my laptop and working on the secondry monitor and it is always connected in. Most of the time, I have to adjust the brightness of the monitor because the display keeps dimming. I have already unchecked the option in Energy Saver menu which automatically reduces the brightness before the display goes to sleep but still it dims after some period of time. Is there anyone solution for this issue? Thanks

[Charites]

There is a very simple procedure to solve this problem. All you need to do is open System Preferences in the Apple menu and then click on Display and then uncheck "Automatically adjust brightness". You can also use the brightness control keys. On portable computers, and if you’re using an Apple LED Cinema Display, they’re usually the F1 and F2 function keys. On some computers, they’re the F14 and F15 function keys. More information is given on this page - http://support.apple.com/kb/PH10969