What Is a Key Light? Learn How Key Light Creates Different Cinematography Effects

A key light is the primary source of artificial light that a cinematographer uses when shooting a scene.

• The key light isn’t a specific type of lighting equipment. It can be anything from a camera mounted flash unit to a lamp.
• When a cinematographer uses more than one source of artificial light in a shot—adding a “fill light” to reduce shadows and/or a “backlight” to outline subjects and create a sense of depth—the key light has the greatest effect on the image, highlighting the subject’s dimensions and form.
• A cinematographer may use multiple key lights in a scene to illuminate a moving subject at specific moments.
• Key lighting started in the film industry but is also now common in photography.

Key lights highlight the form and dimension of on-screen subjects and allow cinematographers to control the atmosphere of a scene. The number of light sources they use, the particular qualities of those lights (color temperature, brightness, etc.), and where they position them can create a wide variety of moods, from mysterious and dramatic to light and optimistic.

Cinematographers use key lighting in a variety of ways, making adjustments to draw out different effects.

• Cinematographers use “hard” (focused) or “soft” (diffused) key light, depending on whether they want striking shadows or a more balanced shot with greater details.
• They position the key at different angles on a light stand relative to the subject depending on the desired setup.
• In the common three-point lighting setup, the cinematographer places the key light at a 30- to 60-degree horizontal angle from the camera to cast interesting shadows across a subject’s face. Thus, if the right side is lit, the left side will be shaded.
• The most common vertical position for the key light is at a 30-degree angle, slightly above the eye line, but cinematographers place the key light higher or lower to produce different effects.
• Natural or ambient light is normally overhead, so when positioned low, the key light appears to distort the actor’s features. This distortion works well in both horror (for a discomforting sense of abnormalcy) and comedy (for laughs).
• When positioned high, the high key light results in more prominent cheekbones and long nose shadows.
• Using just a key light creates a high-contrast scene, especially when no lights illuminate the background.
• If used, a fill light or a reflector decreases contrast and adds details to the dark areas of a scene.
• The key light does not have to directly illuminate the subject. To make a scene more visually interesting, or indicate a subject’s location, a cinematographer may pass its light through filters, screens, reflectors, and obstacles like tree leaves and window panes.
• The key light doesn’t have to be white light, either. Cinematographers sometimes use a colored key with fill lights and backlights of other colors to add more emotional depth to a scene.
• Cinematographers may use indoor or outdoor lighting, and the color temperature (the measurement in Degrees Kelvin) creates different looks. Outdoor lighting is often around 5600K, while indoor lighting is generally 3200K. The dividing line is 5000K, with higher color temperatures over that considered “cool” and blueish, and lower temperatures considered “warm” orange.
• Cinematographers may use the sun or skylight (on an overcast day) as a key light for outdoor shoots, supplementing it with another light source as fill lighting, or vice versa.
• They may also use lamps, lighting fixtures, fires, candles, and other natural lighting sources as key lights if they are of sufficiently bright. Sometimes they even appear in scenes as props.
• While a key light is standard and recommended for novices, cinematographers do not always use one. Excluding a key light can create a cool silhouette effect.

Depending upon the mood a cinematographer wants to create, they use either high key or low key lighting. Each has its own distinct characteristics.

• Low key lighting uses a lot of shadows, darker tones, and deep blacks, with minimal amounts of mid-tones and whites.
• To create the effect, cinematographers often use only a key light, sometimes controlled with a fill light or a reflector. This accentuates the contours of the subject, casting shadows.
• When they use a fill light, cinematographers make sure the key light is dominant, creating a high lighting ratio, such as 8:1 in favor of the key.
• The reduced lighting produces images with the striking contrasts between light and dark known as the “chiaroscuro effect.” This was especially important in moody black and white classics such as Nosferatu (1922) and Metropolis (1927).
• Low key lighting creates a dramatic and mysterious mood and can display a range of deep negative emotions. It typically heightens the viewer’s sense of alienation.
• It is common in dark dramas, thrillers, horror, and film noir.

High key lighting uses a range of whites and light tones, with minimal mid-tones and blacks. The mid-tones become white and the whites become whiter.

• Traditionally, cinematographers achieved high-key lighting with three-point lighting—key, fill, and backlight (also called a “rim light”)—which created a uniform lighting pattern. These days, multiple hot light sources are substituted by much more efficient fluorescent soft lights which provide a similar effect.
• Cinematographers may also use a “ring light,” which creates continuous illumination with few visible shadows.
• High key setups have a much lower lighting ratio, with a balance between the fill and the key that can approach 1:1.
• High key lighting is advantageous because it doesn't require adjustment for each scene, allowing productions to move much more quickly. However, because it doesn’t light certain parts more prominently than others, high key lighting doesn’t add meaning or drama to shots the same way as low key lighting does.
• High key lighting creates an optimistic, upbeat, youthful, light, and airy mood.
• It is common in sitcoms and comedies.

Learn more about filmmaking techniques in David Lynch’s MasterClass.