During an iPhone X demo conducted by Craig Federighi in yesterday's keynote, Face ID appeared to fail to recognize his face, leading to doubts about the feature's reliability and accuracy. 

There was a lot of speculation about just what went wrong on stage, ranging from a Face ID failure to a passcode lock, and according to Apple, it was the latter issue that caused the device not to work properly on stage. In a statement provided to Yahoo's David Pogue, Apple says the device locked after several people interacted with it ahead of Federighi, causing it to require a passcode to unlock.

"Tonight, I was able to contact Apple. After examining the logs of the demo iPhone X, they now know exactly what went down. Turns out my first theory in this story was wrong--but my first UPDATE theory above was correct: "People were handling the device for stage demo ahead of time," says a rep, "and didn't realize Face ID was trying to authenticate their face. After failing a number of times, because they weren't Craig, the iPhone did what it was designed to do, which was to require his passcode." In other words, "Face ID worked as it was designed to."

While Touch ID locks the iPhone and requires users to input a passcode after five failed entry attempts, Face ID only allows for two failed recognition attempts before it locks the iPhone and requires a passcode to access the device, according to developer documentation. There were arguments over how many times Federighi attempted to unlock the iPhone X with Face ID while on stage given that two attempt limitation, but Apple's explanation makes sense. A secondary iPhone X unlocked with no issues during the demonstration. 

The ins and outs of Face ID and its reliability will remain largely unknown until the iPhone X launches in November and is in the hands of customers. Members of the media received hands-on time with the device following the event, but reviews were somewhat mixed. Most people were generally impressed with Face ID and saw it work seamlessly, but there was also at least one report of a problems with the feature not working until the display was turned on and off. 

Face ID uses infrared scanning techniques to create a mathematical model of a user's face, which is compared to a facial scan stored on the device to authenticate. Because it uses infrared, Face ID works in the dark and in low lighting conditions, and Apple says it also works with hats, glasses, and beards, makeup, and other items that might partially obscure the face.

Source: macrumors