On inquiring about how big is a photo 4x6 in a real life situation, it is a bit bigger than most smartphone displays, which means that it has enough room to display details without occupying the space.  Visuals Clipping states that this is a large size that has just enough space to show details clearly without occupying the physical space a lot. Its size is fitting its casual use and the sharing of printed photos. It is also a frequent choice of daily photo printing.