If checked then large bitmaps are divided and processed into smaller pieces. This enables to process bitmaps with arbitrary size and dimension (RTL bitmaps are often very huge). The ‘banding treshold’ option defines the maximum allowed size for a bitmap piece (i.e. if a RTL bitmap size exceeds the ‘banding treshold’, then the banding is applied and each bitmap piece is limited to the ‘banding treshold’ size). If checked, then bitmap banding is applied automatically also in cases where the bitmap dimension is larger than dimension allowed by the system, irrespective of the ‘banding treshold’ size (for example Win9x/Me have only 16-bit GDI and so have limited bitmap dimension).
It is generally recommended to keep the ‘bitmap banding’ option checked (mainly under Win9x/Me systems). Mostly the ‘bitmap banding’ also improves performance.