The iPhone 7 does not feature a telephoto lens. This means the iOS Camera app only uses a digital zoom.
On the other hand, the iPhone 7 Plus does have a telephoto lens. Apple's dual-lens configuration provides a standard lens alongside a second, 2x zoom lens. Photos taken at 2x use this optical zoom for maximum clarity and resolution.The iOS Camera app provides zoom capability up to 10x on the iPhone 7 Plus. Any telephoto zoom beyond 2x uses a digital zoom.