Informal or "asymmetrical" balance is uneven or unequal balance. The objects have nearly the same "visual weight" on either side of the vertical center of the photograph composition, but are different in some element such as size, shape, texture, or value.

Formal balance is equal or symmetrical visual balance. Each side of the vertical center of the photograph has equal weight or exactly the same elements and principles such as shape, texture, value, contrast, etc.