What is Key Light — Definition & Examples in Photo & Film

Key Light Definition

First, let’s define key light

Although it is important to understand other lights such as fill lights and practical lights, the key light definition is the most fundamental lighting term a cinematographer should know. 

Before we define the different effects of lighting, it is important to first define key light. This light can be found in any lighting setup no matter how bright or how dark or where a scene is shot. A solid understanding of the key light definition is a prerequisite to manipulating light to achieve different moods.

What is Key Light in Photography?

What is the purpose of a key light?

The key light works as the main source of exposure for a cinematographer. Key light photography is critical to properly exposing and highlighting the shapes, dimensions, and forms of a subject and atmosphere that appear on screen.

How a gaffer or cinematographer chooses to manipulate or complement this primary light will determine the overall mood of a shot.

There are various film lighting techniques within key light photography that cinematographers utilize to achieve different looks. Commonly, a key light is used in a three-point lighting setup to create cinematic looks. 

The three-point lighting setup is one of the most fundamental lighting techniques to learn. It utilizes key light photography in relation to a fill light and backlight. Understanding the relationship between the three and how to tweak your setup will enable you to create different moods.

The three-point lighting setup, however, is not the only setup cinematographers may use. In addition to the foundational elements of a three-point lighting setup covered in the video, the best cinematographers manipulate other components for different effects.

Some of these components that can be tweaked are the light's color temperature, the angle of the light, the distance of the light from the subject, diffusion of the light, or strength of the light in a set up. 

What kind of lighting styles do DPs create from tweaking these elements? Let’s analyze a few fundamental styles that can be found throughout cinema.

Lighting for Drama and Thrillers

Low-key lighting

Low-key lighting relies on harsh shadows and high contrast, otherwise known as chiaroscuro lighting. In this setup, shadows and deep blacks are more predominant than mid-tones and transitions between highlights and shadows are harsh. For more, watch our video on this lighting style.

A great example of this can be found in No Country for Old Men. The screenplay for No Country for Old Men is dramatic and suspenseful which had to be brought out through the film’s cinematography.

Notice how much of the frame is composed of dark tones and shadows. The high contrast is also a key characteristic of low-key lighting. 

The key light in this setup is typically diffused to allow for a wider spread exposure and softer lighting style. High-key lighting in film is used to create a cheerful, optimistic, and up-beat mood that can typically be found in comedies, sitcoms, or rom-coms.

Both low-key lighting and high-key lighting are defined by the contrast or lack thereof created in a shot from the use of a fill light and a key light. Both, however, require any filmmaker to determine the source of their key light.

Key Light Setup Without Equipment

Natural Key Lighting

Even filmmakers who lack the best video lighting kits have access to one of the strongest key lights in the world: the sun. Natural key lighting in film utilizes natural light sources as a scene’s key light. Key light photography for exteriors often utilizes the sun as the source.

The sun is quite literally the biggest light source a cinematographer can use and it enables filmmakers to create cinematic shots with minimal to no lighting equipment. Natural light is also a key component of shooting any daytime exterior shots.

There are downsides, however, to using the sun as a natural key light. The sun may lead to overexposed shots if shooting midday or close to high noon. The quality of the sunlight can also be inconsistent due to its dependence on the weather. There are a few techniques that can help cinematographers utilize the sun as a key light.

The most cinematic technique is shooting at the first four hours of sunrise or last hour of daylight also known as golden hour. Shooting at golden hour allows for a much softer more diffused light that utilizes the sun as a key light. Cinematographer’s typically use this for cinematic natural lighting, silhouettes, or lens flares. 

Although the quality of the light is softer with overcast weather, it can also be inconsistent depending on the cloud coverage. As Deakins says, it can often come down to a matter of luck and preparation.

Natural lighting often requires the least amount of lighting equipment and is a key element of shooting exterior shots. It is also, however, the most undependable and inconsistent of light sources because it depends so much on the patterns of weather and nature. To address this problem, cinematographers use motivated lighting.

Controlled Lighting

Motivated lighting

Motivated lighting in film uses a controlled lighting setup to accentuate or mimic natural light sources. It is important for any cinematographer or gaffer to establish what the motivation for a light is in any scene. 

The motivation may be the sunlight throughout a window, a practical light such as a lamp, or even the light from a candle. Give the video a watch and take note of the plenty of techniques that can be adapted to cinematography.

UP NEXT

3-point video lighting setup

Now that you’ve learned about the key light and about different methods and techniques that cinematographers use with it, be sure to learn about the complete 3-point video lighting setup in the next article in which we dive deeper into the fill light and backlight.

Up Next: 3-point lighting explained →