Of course, the Google Photos search tool can find people when you search for them. In fact, when you go to the search bar and click to select it, you're immediately presented with three options: People, Places and Things. When you click the More link on the People option, it will show you a picture of every person you have ever photographed -- in order, beginning with the person pictured most frequently.
Click on any of those photos to get all the pictures of that person. When you do that, you'll notice something interesting: Google Photos will show you not only the pictures where the person's face is clearly visible, but also pictures in which the person's face is hardly visible at all.
But unlike Facebook's approach, all the faces that Google Photos search recognizes are visible; I haven't found photos where the person's back is turned.
It's also interesting to note that while Facebook's technology theoretically sounds more advanced, it is still in the research phase and has not been released, whereas Google's search tool is in its shipped product. And it's already available to everyone free of charge.
Google isn't revealing details about how its photo search works, but it probably uses methods that are similar to Facebook's.
One of the most interesting and under-reported features of Google Photos search is that Google has chosen to not associate pictures of people with their identity. For example, when I search for my son Kevin -- who is an active Google user, including a Google+ user -- Google Photos doesn't associate my photos with his identity in its databases.
When I go to Google Photos search, see Kevin's face and click on it, I get hundreds of pictures of him. But when I search for the name Kevin, or for Kevin Elgan, I don't get all the same pictures. Instead, I get pictures that have been tagged or associated with his name directly through mentions on posts.
Obviously, Google could throw an algorithmic switch at any time and start associating people search with identity, but so far it has chosen not to do so.
How Facebook and Google use 'identification by association'
In the old days, facial recognition technology was more straightforward. It would literally analyze faces to look for things like the relative distances between the eyebrows and the nose, and between the bottom of the ears and the chin.
Now, the artificial intelligence behind Facebook's and Google's facial recognition systems is, in fact, recognizing people the way people recognize people. For example, given enough pictures, it actually learns about you. So when it sees your face in one photo, it also makes a note of the setting, the lighting, the clothes you're wearing, your hair and more. When your back is turned and your face is not showing, it can say: "Oh, that's Mike with his back turned."
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