MacBook (Late-2008) screen brightness undesirably varies

The new MacBook displays are relatively bright, because they use the new LED backlighting technologies. As such, in many situations users dim the displays a little, but when they do this the display gives some problems.

Apple Discussions poster Mootarjim writes:

"The brightness on my screen is definitely in a constant state of flux, and it's driving me nuts. I'll set it (at 75%, for example), and then I'll notice a fluctuation, so I'll hit a brightness button, and sure enough, it's set at a much different brightness than I'd just selected seconds before."

This problem resides with the computer's ambient light compensation, which controls both the backlight on the display as well as that for the keyboard. Apple uses an algorithm that brightens the display and dims the keyboard when users are in bright light environments, and does the opposite when the display is in dim-light situations.

In the new MacBooks, the ambient light sensor is in the same location at the top of the screen as the iSight camera (and in fact might be the camera itself). Regardless of the specifics of the sensor itself, the system has software that interprets the ambient light levels and adjusts the display brightness accordingly. It seems that the light sensors on the new MacBooks may be a little sensitive to minor fluctuations in the ambient light, resulting in screens changing their brightness more frequently.

In order to fully address this problem, the software drivers involved with governing the brightness needs to be adjusted, and hopefully Apple will release an update that addresses this issue. However, until then users have two workaround options for the problem.

Workarounds Turn off automatic brightness adjustment In the "Displays" system preferences, locate and uncheck the "Automatically Adjust Brightness as Ambient Light Changes" option. This will require users to manually adjust keyboard and screen brightnesses in lighter and darker conditions. Luckily the manual controls for these features are right on the keyboard, so this option may be preferable for users.

Adjust display brightness to the brightest This problem seems to be more noticeable if users have dimmed their displays slightly, so one option besides turning off the automatic brightness adjustment is to manually increase the brightness of the display using the keyboard controls when this problem occurs. If the display dims again, users can just keep cranking up the brightness manually to its maximum value.

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