Apple's Face ID to support only one registered face per iPhone, will work with most sunglasses

Apple's Face ID allows users to unlock the iPhone X just by looking at it. Face ID will reportedly only allow one face to be registered on an iPhone and will work with most sunglasses.

Apple revealed its tenth anniversary iPhone X at its annual event on September 12 with the much-hyped Face ID feature. Face ID allows IPhone X users to unlock their device simply by looking at it. According to TechCrunch, the Touch ID feature will allow only one face to be registered per device, while setting up the phone.

The one face per phone limitation can result in some inconvenience for users who would like to share the iPhone X, however, the secondary passcode feature is still an option. In order for the Face ID to work, the iPhone X makes use of an infrared camera along with a dot projector that creates a 3D model of the registered face. The smartphone sports a flood illuminator which enables the Face ID to work in the dark as well. Apple claims that Face ID improves each time when the user’s face is scanned thanks to machine learning. 
Keith Krimbel via Macrumors tweeted saying that he emailed Apple’s VP of Software Engineering, Craig Federighi. He asked him about the details of iPhone X’s Face ID. Krimbel asked if the Face ID works with sunglasses and what if a thief steals the phone and points it at its user? Federighi replied saying that the Face ID will work with most sunglasses as they allow enough IR light for the feature to work, however, he did point out that Face ID would not work with all sunglasses.
He answered the second query saying that if a user does not stare at the phone directly, Face ID will not work. Federighi also revealed an interesting feature that will quickly disable the Face ID. A user needs to grip buttons on both sides of the phone to temporarily disable the Face ID.