- comprise the Cartesian axes on an Euclidean plane (photographs and paintings are generally presented in two dimensions); and
- become the frame of the viewfinder.
These are the most comfortable for us to view. This is because our natural field of vision is biased towards:
- scanning from side-to-side; and
- perceiving horizontal depth,
There is a higher energy cost for us to perceive in the vertical plane. Scanning from top-to-bottom and perceiving vertical depth often necessitates a tilt of the head: a weighty structure whose stable articulation under gravity consumes not inconsiderable energy. Vertical lines convey a sense of movement, speed and energy: of something falling due to gravity or moving to overcome its effect.
Horizontals and verticals in combination
Horizontal and vertical lines complement each other because they:
- act as natural stops to each other's movements; and
- create balance, of an upright being supported by a baseline.
When using these Cartesian axes, attention must be paid to align them exactly with the image frame, because their easy comparison renders misalignments glaringly obvious.