Apparently Face ID uses an Infrared Camera which will work with some Sunglasses, but with specific pairs, particularly Polarized/Iridium Oakleys that block more IR, it can’t scan the face confidently enough to unlock. Included a quote below explaining it.
“It turns out that polarization isn’t the issue — I have a set of polarized sunglasses that work just fine with Face ID. What it is is that different lenses have a different amount of infrared filtration. Most let enough IR through that through most lenses your eyes are visible to IR even if they’re not visible to the human eye,” says Federighi. “There are some lenses whose coatings block IR. In those cases the customer can just use a passcode or take them off.”
Anybody here have the iPhone X and experienced this? Would argue it’s a nice differentiator of higher quality sunglasses!
Source for quote above: Interview: Apple’s Craig Federighi answers some burning questions about Face ID