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Key light

The key light - a vital player in the three-point lighting setup.

What is a key light?

Roughly speaking, the key light is the primary light source in a frame/shot. The key light is one of the building blocks in lighting for photographers and cinematographers alike. You can find this type of lighting in both low and bright conditions in your shot.

The key light is a part of the three-point lighting setup along with the fill light and backlight.

Graphic of the three-point lighting setup.
Three-point lighting

A solid understanding of key lights will guide you in manipulating lights to create different moods in your image. Factors such as strength, color, and angle of light surround the definition of key light itself.

You will most likely place key lights before your subject, wrapping them in light. Keywords include low-key, medium-key, and high-key.

  • Low keys will expose the lower tones
  • Medium key will show the medium tones more
  • High key will expose your high tones

Each type of key will give a different feeling to your photos.

You can also manipulate the angle of where the light is coming from to achieve different effects. As you can see, the key light plays an important role in photography. Let’s explore its purpose in more detail.

What is the purpose of a key light?

As explained above, the key light acts as the main light source in a shot.

As mentioned, within key lighting, photographers will commonly use a three-point lighting setup for cinematic-style looks. As one of the most important lighting techniques in lighting, a three-point lighting setup is a combination of the key light, fill light, and backlight.

A firm understanding of this concept will affect your capabilities to change your lighting and give you access to different moods.

Take note!

Although this isn’t the only type of lighting that photographers and cinematographers use, it serves as the lighting basis.

After that, photographers mix and match the other components, such as lighting color temperature, the distance between light and subject, the angle of light, diffusions, and, lastly, the strength of light.

To sum it up, the key light orchestrates the atmosphere/mood for a shot. It works in tandem with fill light and backlight to achieve cinematic looks.

What is low-key lighting?

Low-key lighting further emphasizes the harsh shadows and high contrast an image/setup might offer. This setup brings out the deep shadows and solid blacks, making transitions between both shadows and highlights harsher. You rarely see a lighthearted scene in a movie using this type of setup.

Although the low-key lighting does the complete opposite of the high-key, it doesn't necessarily make a gloomy and sad photo 100% of the time. Low-key lighting creates a dramatic and mysterious atmosphere, making it interesting and edgy.

Suspenseful scenes often feature dark tones and an abundance of shadows, which are the main characteristics of low-key lighting. These scenes will use a minimal amount of fill light possible. The ratio between the key light and fill light will usually fall around 8:1. This ratio will result in hard lighting, which in turn makes harsh shadows (which further adds suspense/drama).

Girl wearing black hat and outfit in low-key lighting.
Portrait using 8:1 lighting ratio for low-key lighting

Overall, the low-key lighting will set the stage for horror, thrillers, or serious and dark drama. The best example is the movie Joker. This 2019 masterpiece uses low-key lighting to its advantage and further emphasizes the dark, chilling atmosphere. I could get into an essay of appreciation in Joker (2019), but maybe next time.

Scene from Joker movie.
Joker using low-key lighting

What is high-key lighting?

Ah, yes, high-key lighting. Most images and movies use high-key lighting to elicit a more optimistic, light-hearted, upbeat reaction from the audience. This setup is much softer and brighter than the low-key lighting. It incorporates a minimal amount of shadows and contrast and adds more highlights to the mix.

This light setup uses a ratio of around 1:1 (Key vs. Fill), which pretty much eliminates shadows from the scene/shot since they use soft light that envelopes the subjects in light.

Man standing on beach with bodyboard in high-key lighting.
Portrait using high-key lighting

In cases where the shot is done outside, they will most likely rely on the sun and clouds to achieve the diffused light. The clouds become a natural yet huge softbox to diffuse the sun's usual hard light.

It’s difficult to do, but it’s worth the effort. Overcast weather will make the quality of the lights much softer, although it may be quite inconsistent because they are exterior shots.

Not quite reliable and dependable, which leads photographers to use controlled lighting.

Where is the key light placed?

Key lights can be adjusted to be hard or soft, depending on your setup and how you want the end result to look. For the most used setup (three-point lighting), the key lights are adjusted at a 30-60-degree angle.

For example, in this fitness portrait session I did, you can see I placed it at a 30-degree angle from my subject:

Woman standing in boxing gym with key light at a 30-degree from her.
Key light at 30-degree angle from subject

The key light will often hit the front portion/smart side of your subject. It doesn’t have to be exactly like this, but it allows the fill light to help smoothen the look. It can also be placed at a high or low angle to produce various effects. Usually, photographers will position the lights above the eye line.

This is done to prevent any distortion of the subject's features. Your natural ambient lighting will most likely come from overhead. On the other hand, the placement of key lights at a low angle reminds me of horror movies. You know, the scenes where the subject's face is lit from below.

How do you use a key light?

In a three-point lighting setup, you will use the three elements below:

  • Key Light for the primary lighting
  • Fill Light to fill the opposite part of the key light
  • Backlight for rim light effect or to give a three-dimensional feel

With that being said, place your key light where you want to have the most illumination on your subject. For example, if you're going for a Rembrandt lighting look then place at 45-degree angle from subject. If you're going for a side lighting look then place at 90-degree angle from subject.

Remember that you can also use a softbox or umbrella to make your key light a soft light instead of hard light.

Guy sitting on stool in studio getting picture taken.
Using softbox key light at 45-degree angle for Rembrand lighting

How bright should key light be?

Well, it depends on the setup that you want to achieve. The key light definition is basically the main source; the brightness can be rationed for either high-key or low-key.


The general key-to-fill ratio is at least 2:1, which means that your key light should be at least twice the brightness of your fill light.

This ratio gives you mainstream-looking lighting for filmmaking and YouTube videos.

Avoid using a 1:1 ratio unless you are consciously aiming for the look. Otherwise, your video might look flat and lack any dimensional benefits.

Difference between fill light and key light?

To start off the key light vs. fill light debate, I guess it’s fair to say that you can’t compare them as equal rivals. The definitions and importance are different in the beginning. Fill light is used to lift the shadows from your frame.

It is less powerful than the key light and decreases contrast from your subject/object. Fill helps them to bring out the details that would usually be left untouched. On the other hand, the key light is used as the main illumination source.

Mannequin head being lit by key light.
Key light only
Mannequin head being lit by key light and fill light.
Key light and fill light

From the get-go, both of these lights have different purposes. Now, let’s move on to their usage in ratios. When setting the light intensity, the key light is prioritized over the fill lights. Since fill lights hold a more supplementary role, they are always used at a low intensity and are usually half of the intensity of key lights.

In conclusion, here's a recap:

  • The key light is used as the main light source in cinema and photography. Its main purpose is to affect the overall mood and atmosphere of a shot.
  • Low-key lighting is a setup that enforces shadows and contrasts. It makes the shot appear more serious, mysterious, and edgy. The ratio used to achieve this setup is generally an 8:1 Key to fill ratio.
  • A high-key lighting setup eliminates the shadow and contrast. It makes the scene appear more lighthearted and is often used positively. The key-to-fill ratio used is usually 1:1 or 1.5:1.
  • The key light is used as the main illumination source in three-point lighting. It is commonly positioned at a 30-60 degree angle overhead or over the eyes at minimum.
  • Key light should be used as the main source of illumination, normally supported by fill and backlight. The intensity of light should be adjusted based on the specific needs/requests of the photographer/client.

Lighting is the main aspect that will make or break your composition and concept. Studying and amassing knowledge is important, but it won’t be enough if you don’t put the theories into practice. Have fun!

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