Gestalt theory embraces a number of grouping principles as "laws" of perceptual organization. We need to be aware of these principles as we photograph.
Proximity
Objects or shapes that are near one another appear to form groups. Even if the shapes, sizes, and objects are radically different, they will appear as a group if they are close together.
The closer the objects, the stronger the gestalt. In rank, from weakest to strongest:
Similarity
Elements of the visual field that appear to be similar in some way are grouped together. We group elements based on similarity in
Continuity
We have a preference for smooth continuity of lines over discrete, irregular, abrupt changes. Thus the eye will continue on a smooth path, even beyond its ending point to find an adjoining object.
Stated another way, once set in motion, the eye will continue in that direction until something significant is found. Thus our eyes have a tendency to follow the lines of a photo until interrupted.
Closure
The mind seeks to complete an object when pieces of the object are missing or obscured. We concentrate on "closing" objects or shapes that are incomplete, especially those objects that are familiar to us. With unfamiliar objects, the mind must work hard to fill in the gaps.
Incomplete shapes are generally more interesting than completed ones, since they require our participation to finalize.
Common Fate
We group together objects moving in the same direction. Two people walking toward the left will be seen a unit.
Simplicity
Given multiple interpretations of the same data, we prefer the simplest and most stable configurations. Often we base our choices on symmetry, regularity, and smoothness.
Other equally debatable grouping principles