Comment by Mankaninen

While f/64 sounds like a small aperture, it can be worth remembering that it was on large format cameras. A small sensor like on iPhone 6 is wide open corresponding to depth matching f/113! (iPhone6 is f/2.2, crop is 7.21, 8"x10" camera is crop 0.14. 7.21/0.14*2.2 = f/113)