eli5: How do tech companies do it so that face ID doesn’t recognize a picture of that person?

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(edit: for the purposes of this question I’ll only consider Apple’s Face ID system but thank you to everyone who addressed Android and others) 🙂

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24 Answers

Anonymous 0 Comments

There is a time lag between features on a face because since parts are closer and others, farther. If they all come back the same it won’t work as the face is now not a match to the one on file.

Anonymous 0 Comments

As someone who has never used face id for anything, does it not work with a picture? Are you telling me that every TV show and movie where they used a photo of someone to unlock a phone was lying to me?

Anonymous 0 Comments

There is a time lag between features on a face because since parts are closer and others, farther. If they all come back the same it won’t work as the face is now not a match to the one on file.

Anonymous 0 Comments

It projects a grid of dots, and the sees how they lie in your face. It then gets a good impression of the depth of the features as well as the flat image

Anonymous 0 Comments

There is a time lag between features on a face because since parts are closer and others, farther. If they all come back the same it won’t work as the face is now not a match to the one on file.

Anonymous 0 Comments

Face ID doesn’t just simply take a picture of your face, it uses an infrared projector to project dots on your face and then an infrared camera sees those dots calculates where those dots are in 3D space. For example if you were to hold up the face ID sensor to two objects, one further away from the other it can determine with certainty which one of the 2 objects is closer and which one is further.

If you were to just hold up a picture of a person, it will project the dots on top of the picture and see that it is entirely flat and therefore is not a face.

[Here’s an example of what the projection of the dots look like.](https://i.ytimg.com/vi/g4m6StzUcOw/maxresdefault.jpg)

Anonymous 0 Comments

As someone who has never used face id for anything, does it not work with a picture? Are you telling me that every TV show and movie where they used a photo of someone to unlock a phone was lying to me?

Anonymous 0 Comments

Face ID doesn’t just simply take a picture of your face, it uses an infrared projector to project dots on your face and then an infrared camera sees those dots calculates where those dots are in 3D space. For example if you were to hold up the face ID sensor to two objects, one further away from the other it can determine with certainty which one of the 2 objects is closer and which one is further.

If you were to just hold up a picture of a person, it will project the dots on top of the picture and see that it is entirely flat and therefore is not a face.

[Here’s an example of what the projection of the dots look like.](https://i.ytimg.com/vi/g4m6StzUcOw/maxresdefault.jpg)

Anonymous 0 Comments

As someone who has never used face id for anything, does it not work with a picture? Are you telling me that every TV show and movie where they used a photo of someone to unlock a phone was lying to me?

Anonymous 0 Comments

It projects a grid of dots, and the sees how they lie in your face. It then gets a good impression of the depth of the features as well as the flat image