One thing really jumped out at me yesterday reading Mashable’s early review of the iPhone X, and that was Apple’s response to a query by Lance Unlanoff.

One important limitation of Face ID: It only lets you register one face. That may strike many as unnecessarily limiting since Touch ID lets users register up to 10 [sic] fingerprints, but Apple says it found the number of people who register more than one person’s fingerprints is miniscule.

The idea that hardly anyone registers more than one person’s fingerprint didn’t ring true to me, and our poll shows that it’s not true for 9to5Mac users at least …

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At the time of writing, the majority of our readers have more than person’s fingerprints registered for one or more of their iOS devices. Almost half (48.98%) have one other person registered, and a further 6.85% have more than two people.

Convenience was the most common reason – for example, being able to access the Music app on your partner’s phone while they are driving.

I have my fingerprint registered on my device, my wife’s device, and my 12 year-old’s. My wife has a fingerprint registered on my device as well. I imagine lots of husbands and wives and/or parents and children have this setup for convenience.

Parental control of kids’ devices was another one.

Many people have multiple kids, and we all have enough passwords to remember that we shouldn’t have to do this with our kids phones.

Emergency access to other family members’ phones was a third reason cited. Although anyone can make a 911 call on a locked phone, there are other types of emergency where someone may need to urgently call a local doctor, school, family member or similar.

We have not had a home phone for about 10 years, and our cells are it. My son has a fingerprint in my and his mom’s in case of emergencies.

While it’s true that 9to5Mac readers are not necessarily typical of the iPhone-owning population as a whole, in this area I don’t think we’re so different from anyone else.

Which then raises the question: why is Face ID limited to recognizing a single face? There has to be some reason for Apple to take away an existing feature – biometric login for more than one person – and the claim that it is used by hardly anyone doesn’t seem to withstand scrutiny.

It seems to me that there has to be some technical reason for this – and I think there’s a clue in an Apple support document for Touch ID.

Enroll up to five fingerprints. Each new print might make fingerprint recognition take slightly longer.

So, recognizing a fingerprint of course takes time, and having to check for multiple fingerprints naturally takes longer. Apple says ‘slightly’ longer, but it’s enough time that the company feels it has to warn about it in a consumer-facing document.

Face ID is clearly a bigger technical challenge than Touch ID. Face ID requires the iPhone X to construct a 3D model of our face, and compare it to a stored one. Given that Apple says Face ID can cope with different angles, different hairstyles, different clothing, different jewellery and so on, it’s clear that there’s a fair amount of processing power involved.

My guess is that doing all these checks for more than one person would make face-recognition noticeably slower than Touch ID, and Apple was concerned that reviewers and consumers alike wouldn’t respond well to that. That, I think, is the real reason Apple limits Face ID to a single face.


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