Night mode is an automatic setting which takes advantage of the new wide-angle camera that's in the iPhone 11 and 11 Pro models. It's equipped with a larger sensor that is able to let in more light, allowing for brighter photos when the light is low.
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Apple Fixes FaceTime on Older Versions of OS X, iOS 6 Still Not Working
Apple, however, has not yet addressed the problems with FaceTime that are in iOS 6. While it is encouraging that Apple released an update for FaceTime for OS X 10.6, Apple support's recommendations for iOS 6 users has been to upgrade to iOS 7. One user has quoted Apple support as saying that the only fix for iOS 6 is to upgrade to the latest version of iOS 7, with no current plans to release a fix on iOS 6 or iOS 5.
According to Apple's updated FaceTime troubleshooting page, users who are still having trouble with the application are recommended to update to the latest version of iOS or OS X.