Dominance of shape, size and value, etc., will determine which bits of information will be perceived as figure and which will assume the subordinate status of ground. While the ground, or ‘counter-from’, shares in the form of the figure, the latter generally has a shape or object quality that seems to visually reside in front of the ground.
See also: Footprint – Interaction – Positive-negative space –Reciprocity Filter
The sunlight did not know what is was before it is a wall. --- Louis Kahn
A filter is an intercepting screen that controls the passage of whatever medium passes through it. Like the filter on a cigarette that is intended to remove impurities in the inhaled smoke, it is a device that, in order to achieve the desired outcome, separates out and entraps the unwanted. The term has many ‘screening out’
For example, it can be a controlling device used in people-moving or traffic segregation, a screen for modifying or absorbing light or for controlling views, or a diagrammatic sieve used for flushing out ideas.