How does the iPhone 7 plus dual camera work?

Question

I just bought the iPhone 7 plus and of course the first thing i tried was to take some pictures with the new dual camera.

I was then wondering how the transition between the two cameras works since while zooming it looks as smooth as the standard digital zooming on any other phone.

So i tried to put a finger in front of only one camera to check when the transition occurs. If you put the finger in front of the right camera (watching the screen) you see your finger no matter how much you zoom, if you put your finger in front on the left camera then you will never see the finger.

At this point i thought that maybe the preview was taken only from the right camera and then when you actually take the picture it gets the image from one or the other according to how much you zoom.

But the picture that i took gave the same result that the preview did, finger on the right camera -> you get a black picture, finger on the left camera -> you get the image without the finger, no matter how much you zoom.

How does it work? Is it an issue with my iPhone or do i just not get something?

Thank you everybody!

EDIT:
I tried both pinching the screen to zoom and using the "1x" button to activate the "2x" zoom, and i got the same result

Answer 1

I did a simple test to see how this actually work by actually covering the camera in the left (the telephoto lens). I found this pattern: in low lighting the iPhone will always use the wide angle lens (on the right) and digital zoom. Other cases the iPhone will switch to the telephoto on zooms greater than 2x. The iPhone didn't switch to the telephoto when you're covering the lens is because when you cover up the wide angle lens it tricks the iPhone into thinking that it is in low lighting so it will use digital zoom instead.

Answer 2

You're probably just using the digital zoom and never switching cameras. You describe the zoom as "smooth" - this sounds like you're not switching cameras.

To switch between the cameras, press the "1x" circled button and it will show "2x". This is the secondary camera.

You can do digital zoom on either camera afterwards.

Answer 3

Low-light photos are so much better than they used to be, since the Camera app can combine data from both lenses, the optical image stabilization helps keep things steady, and the wide-angle lens’s f/1.8 aperture lets in a lot more light than the f/2.2 lens in the iPhone 6s,The new Portrait mode coming to iOS 10.1 is a great example of what the iPhone 7 Plus’s exclusive two-lens camera system can do. Since this mode is still in beta (both the feature itself, and iOS 10.1, are in beta as of this writing)