Accent lighting in film production is defined as a light unit that highlights one specific subject or object. Examples of an accent light include a fill-light or a key-light. The use and relevance of this film-lighting tool is to draw attention to a single place on the set or screen. The use of accent lighting can be subtle or obvious to the viewer.
Backlighting is an obvious and creative lighting technique used during a film's production. This method of lighting sets a light behind an actor or object to illuminate the silhouette of that subject. In some cases this will produce a halo ambiance around that subject, while simultaneously not illuminating the front of the subject. This lighting approach can create an element of wonder, suspense or ambiguity for the audience, as they are unable to fully determine the subject.
These two terms refer more to the intensity and strength of the lighting used during a specific scene. Low-key lighting is less intense lighting that often produces shadows and darker settings. This technique usually corresponds with dramatic or suspenseful moments in the film. High-key lighting is bright and diminishes contrast, as compared to low-key lighting. This method more fully illuminates and does not cast shadows.
These two lighting techniques are usually used in conjunction. The key light is usually placed at a 45-degree angle between the subject and camera. The key light serves as the main light on a subject. Comparatively, the fill light is used to illuminate areas that are not lit by the key light. The fill light is generally at the side of a subject, and this helps to dampen shadows.