Originally Posted by infrequent
Yes the secondary (56mm) lens is only engaged if you choose the Portrait mode but in practice if its engaged, it typically stays in that mode until you change it back. For example if you picked Pano option and shot one, the next time you invoke the camera app it is in Pano mode. Presumably this will hold true until the app state memory is cleared or the phone is switched on/off.
That hasn't been my experience with the iPhone's camera, but maybe I don't use it frequently enough for it to remember. Of course I tested the 7 plus in the store and it wouldn't even remember the 2x function when I hit the home button and immediately went back into the app. Really, I wanted it to work for me.