Field guide
Gallery mat proportions for photographs
A gallery mat is negative space that separates image detail from the outer frame. Its proportions should respond to the print and viewing distance, not a universal percentage.
01
Begin with the shorter print dimension. A mat around eight to fifteen percent of that side is a useful inspection range, then adjust for subject density and final frame size.
02
A slightly wider bottom edge counters the optical impression that an exactly centred picture is sinking. The adjustment is usually subtle rather than a conspicuous caption area.
03
Keep the visible opening just inside the print edge for physical mounting. A digital mock-up can show the whole photograph, but a real mat needs overlap to hold paper safely.
04
Judge the mat beside the wall colour and frame profile. Bright white, warm cotton and black cores alter perceived contrast even when their geometry is identical.