This is almost entirely due to sensor size. The sensor on the iPhone is smaller than your pinky nail with pixels between 1µm and 2µm in size (depending on which

This is almost entirely due to sensor size. The sensor on the iPhone is smaller than your pinky nail with pixels between 1µm and 2µm in size (depending on which camera is used), the Nikon on the other hand has pixels over twice the largest size on an iPhone.