Тelephoto zoom? The iPhone X needs just a quarter of the 7 Plus light for it

Ever since Apple introduced its first dual-camera phone, the 7 Plus, it has been giving us a cropped version of the wide-angle camera at the touted 2x magnification when the light is dim, as the telephoto lens has narrower aperture, and a zoomed-in picture with it just wouldn't come out as good. 

The amount of light needed for the telephoto to get engaged in an "optically" zoomed photos is decided by the camera algorithms, and varies with each situation, so a photog decided to measure if there is any difference between the 7 Plus, and Apple's latest and ...