The screen can only be rotated up to 90° before it repeats itself. The rotation angle away from the vertical axis is known as the screen angle. When the screen is aligned parallel to the paper edges, the screen angle is said to be 0° or 90°. The vertical and horizontal distance between successive dot centers is constant and is a function of the screen frequency.
With the exception of FM (stochastic screening), all screens consist of dots arranged in a regular pattern or matrix.
