Every visual presentation involves figure-ground relationships. This relationship between a subject (or figure) and its surrounding field (ground) will evidence a level of contrast; the more an object contrasts with its surrounds, the more visible it becomes.

When we create visuals that are intended to be read, offering the viewer enough contrast between the background (paper or screen) and the text is important. Text presentations ideally offer at least an 80% contrast between figure and ground.

(Black text on a white background is ideal.) If there is not enough contrast between figure and ground, a viewer will squint to view the text, causing eye fatigue.

An occurrence known as 'simultaneous contrast' may happen when opposing colors are placed in close proximity to each other. Text may appear to vibrate, or cast a shadow. Eye strain and fatigue will result if a viewer focuses on a document displaying similar properties for an extended time period.