Mavericks detects motion via light sensor to prevent system sleep

OS X Mavericks (Desktop, MacBook)

Concerned Mac users took to Twitter this morning following the revelation of a chunk of code found in OS X Mavericks update that resets idle time when the computer detects motion. They feared this meant the iSight camera is ‘always watching.’

But as it turns out, that’s not the case at all. The code, which was first spotted by Moshen Chen of Radiantlabs, actually makes clever use of the light sensor positioned to the left of the iSight camera by interpreting “changes in light” as movement…

The Verge reports:

“The sensor is already used to adjust screen brightness to ambient light, but the new OS puts it to a different purpose, tracking changes in the light as “movement,” and resetting idle time accordingly.Verge tests confirmed this on two separate Mavericks laptops: after covering the camera but not the light sensor, we were able to delay sleep mode by changing the ambient lighting conditions.”

Users have always been able to manually set a time limit for when their Macs would go to sleep based on halted physical interaction with the computer like typing or moving the mouse. But Mavericks takes things a step further, improving the feature’s accuracy.

Apple released OS X Mavericks to the public as a free update on October 22nd.