[nf8nnfufuu]

What happens to unknown faces in photographs, you just discard them? What if I have 1000s of photo of aunt Emma, but aunt Emma is not on Facebook. When she eventually joins, and turns Face recognition on, will you rescan all my old photos to identify her? Or will Face recognition only work for new photos?

[pesenti]

We don't discard anything because we don't specifically identify or recognize these faces in the first place.

I don't think we go back to old photos, I suspect it would not be practical. But I am not positive on this one.

[plmpsu]

What do you mean by not specifically identifying or recognizing these faces?

When a face -- which is unknown to Facebook -- is found in a photo, is that face used for graph building? Is a anonymous representation of it kept?

[pesenti]

No: https://news.ycombinator.com/item?id=20903110

[nf8nnfufuu]

Don't you have to try to identify a face first, before you can decide you don't want to identify it? I don't see how it can work if you don't try to identify every face.

[pesenti]

You identify that there is a face yes, that's face detection, https://en.wikipedia.org/wiki/Face_detection, which is not the same as face recognition and doesn't need a model per person.

[nf8nnfufuu]

No I mean you have to try to recognize the face. Otherwise you can not decide whether the face is from a person who wants to be identified or not.

I don't see how it could work any other way.