The 7 Plus has two camera lenses: one wider angle, one a 2X zoom. Clever software lets users blend the zoom to any degree between them (or, using digital zooming, go all the way up to 10X).
But when Apple first introduced the 7 Plus, it said that the two-lens setup has a second benefit: It lets the camera tell the foreground subject apart from its background.
And with that knowledge, the phone can create a soft blurry-background look. Ordinarily, users see the new look only in professional photos, or at least photos taken with big black SLR cameras using high-aperture lenses (f/1.8, for example).
Today, users can download the iOS 10.1 update for their iPhone 7 Plus that gives it a beta version of the new Portrait mode. (Open Settings -> General -> Software Update, and click Install.)
Now, the blur in this case is not optical, the way an SLR makes it. This is a glorified Photoshop filter; it’s created with software.
And Apple’s not the first company to try it. Some Samsung phones, years ago, offered a similar feature. But without dual lenses, those phones didn't have great luck distinguishing the subject from its background, and you often wound up with hideous “leaking” of the blurriness effect.
Apple's effect on the other hand, generally looks great, even when the outline of the subject is complex (like frizzy hair). The blur occasionally looks a little phony, as in the building outlines shown here, but at least it never spills out into the subject's beloved’s face. (It does occasionally leak into non-human subjects. Maybe that’s why this feature is still called beta.)
To use the portrait mode, users should be aware that the new feature shows up as one of the modes in the Camera app.
Users just point the camera at someone who’s standing between 15 inches and 8 feet away, and boom: They see the background blur, in the preview image. Take the shot. That's all there is to it.
If a second person is standing within the 8-foot range, they can tap the screen to make that person the subject.
In Settings -> Photos & Camera, users can turn on "Keep Normal Photos" for this depth effect. It means, "For each Portrait photo I take, save two images—one with, and one without the blur."