Brother DCP-4020C - Manual (Page 90)

PRINTER DRIVER SETTINGS 8 - 12
Halftone Pattern
The DCP can use two methods (Diffusion or Dither) to arrange
where to place dots to express halftones. There are some predefined
patterns set for this and you can select which one to use for your
document. Select the appropriate method.
■ Diffusion: Dots are placed at random to create the halftones.
This method of printing is more suitable for printing photographs
that have delicate shades and graphics.
■ Dither: Dots are arranged in a pre-defined pattern to make
halftones. This type of printing is more suitable to printing
graphics that have definite colour boundaries or for printing
charts such as business charts.
Some halftone settings cannot be selected with certain
combinations of Media Type and Quality selections.