Light tends to be an aspect whose relevance varies wildly. In some works it is hugely significant. In others it’s an important supporting element, while in still others you may not need to consider it very much at all.
On a practical level, light defines form and edges. In a painting depicting naturalistic forms, the intensity and brightness of the light depicted can provide ambiguity, drama, softness or clarity. Over-bright light can make a painting seem clinical or bare; dramatic shadow lends a sense of tension and mystery.
When analysing light, keep the artists’ medium in mind. Oil paint is admired for the deep luminance it lends colours, allowing subtleties of shadow and soft highlights. Oil paint allowed the famous sfumato effect of Leonard da Vinci’s paintings. Fresco by contrast cannot hold a sheen on its surface, and the difficulty of mixing colours on its quick-drying surface lends itself to clear, sharp light. Watercolour can be chosen for its softness and haziness. The effect of light achieved by the artist is therefore often connected to the medium chosen, and these limitations become particularly important when critiquing naturalistic works.
Light also creates interest and focus. Where is the light coming from, and where does it fall? The eye naturally follows the light around the work and skims over shadowed areas, so light and highlights create focal points in a composition. Depicting someone in shadow or a spotlight changes the viewer’s immediate perception of them, and contributes to their characterisation. In religious works deities may be portrayed as a sun or a ray of light.
In some works, most notably those of the Impressionist painters, light itself is the main subject. Some modern art, like light shows, might be made up of light: others might explore the way light reacts to other elements, or manipulate it as part of the viewer’s experience. Even in statuary, light may be significant. The finish given to the medium determines the way light behaves upon the surface, and depth and sharpness of modelling play with light in different ways. Thick curls and other complex details, for example, which trap light, can be contrasted with a high polish. This sort of visual variation is an important feature of the Baroque style in statuary.
Light, whether within a work or outside it, is omnipresent. It is connected to style, symbolism and the viewer’s experience, as well as many other aspects. But while it is significant, it is rarely the star act.