When we view a painting or photograph, our eyes travel from left to right and we typically begin viewing an image at the bottom left and then move upward and to the right. With this in mind, many works of art are composed in a triangular manner that is meant to draw our eyes to an area of focus within a subtle triangle shape.
The Golden Triangle
In ancient Greece, art was meant to be as perfect as possible, and mathematicians of the era concluded that any work of art needed to have a specific compositional balance in order to please the eye. This led mathematicians to devise the "Golden Triangle" or "Golden Mean," in which artists divided a canvas into eight equal segments, horizontally and vertically. An artist would count five stops from the left and then from the right, and five stops from both the top and bottom. The triangular area in the resulting middle area was meant to be the focal point of the painting.
Shape and Meaning
The shape of a triangle is made up of two diagonal lines that are anchored on a horizontal line. In a painting or photograph, a triangle will guide our eye to the triangle's three separate points. The image or figure at the peak of the triangle will appear to superior to other images; if the triangle is reversed, the figure at the bottom will appear inferior. A triangular composition can help make an image more coherent and the form appear more dynamic.
Simple geometric shapes within a painting or photograph can help strengthen the composition. A triangle is one of the strongest compositional shapes, as it can add a sense of visual unity. In essence, a triangle is a closed curve incorporating at least one diagonal. Since the curve is closed, it won't lead the eye outside of the frame. A single triangle in in the middle of the frame can lead to a somewhat static composition, but triangular composition can be found in many famous works of art.
The Mona Lisa
When painting portraits, many famed artists throughout history would set a figure on a horizontal plane to create a three-dimensional triangular composition. This was certainly the case with one of the art world's most famous paintings, Leonardo da Vinci's Mona Lisa. In the painting, Mona Lisa takes on a three-dimensional quality because she is placed in the center of the composition. She is depicted as broader at the base, occupying the painting's foreground, while the background recedes in depth, causing her to take on the shape of a pyramid.