It is much easier to get a bunch of stuff precisely arranged and uniformly lit when it is lying flat. Especially if you flatten it out by placing a sheet of glass over it.
With everything standing up on end you're constantly fighting gravity and air currents, as well as problems like background art painted using water-based media that makes the paper it's on want to wrinkle. Much easier to just squish it all flat with gravity's help.
With everything standing up on end you're constantly fighting gravity and air currents, as well as problems like background art painted using water-based media that makes the paper it's on want to wrinkle. Much easier to just squish it all flat with gravity's help.