What is Key Light? Everything You Need to Know

This is a guide covering key light.

In this glossary definition you’ll learn about:

You are having a date with your SO, but suddenly the light becomes cold white. It ruins the mood and makes everything awkward, leading both of you to say goodbye a couple of minutes in.

It just shows that lighting has been and will continue to be relevant in every aspect of our lives.

Especially in photography, where the main goal is to tell a story through a well-executed concept. This leads us to the topic of today, key light.

Let’s dive in.

key light

What is Key Light?

Roughly speaking, the key light is the primary source of light 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.

A solid understanding around key light will guide you in manipulating lights to bring forth different moods to your image.

The Key Light definition itself is also surrounded by factors such as strength, color, and angle of light. You will most likely place key light in front of your subject, wrapping them in light. There will also be a term such as low key, medium key, and high key.

Low keys will expose the lower tones, the medium key will show the medium tones more, while the high key will expose your high tones. Each type of key will give a different feeling to your photos. Read on for info about the low and high key light definition below!

You can manipulate your lighting by:

  • Softening it using a diffuser or bouncing the light off your surroundings.
  • Adjusting the location of your subject farther from the light to create more defined shadows.
  • You can also manipulate the angle of where the light is coming from to achieve different effects.

As you can see, key light holds an important role in the world of photography. Let’s dive in deeper to give you a better understanding of its purpose.

key light
Photo by KAL VISUALS

What is the Purpose of a Key Light?

As explained above, the key light acts as the main source of light in a shot. It’s this degree of importance that forces gaffers to accurately expose and highlight dimensions, forms, shapes, and atmosphere of the image.

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 lightings and give you access to different moods.

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

After that, photographers will mix and mash the other components such as lighting color temperature, distance between light and subject, and 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 that an image/setup might offer. This setup brings out the deep shadows and solid blacks, making transitions between both shadows and highlights harsher.

You will rarely see a lighthearted scene in a movie using this type of setup.

Although the low key lighting does the complete opposite of 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 while also being edgy.

Suspenseful scenes will often consist of dark tones and an abundance of shadows. Both of those components 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, that in-turn makes harsh shadows (which further adds the suspense/drama).

Overall, the low-key lighting will set the stage for horrors, 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.

What is High-Key Lighting?

Ah yes, high-key lighting. Most images and movies will use high key lighting to draw out a more optimistic, light-hearted, upbeat reaction from the audience.

This setup is much softer and bright when compared to the low-key lighting. It incorporates the minimal amount of shadows, 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 the existence of shadows from the scene/shot. Since they use soft light that envelopes the subjects in light.

In cases where the shot is done outside, they will most likely rely upon 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.

high key lighting
Photo by Samuel Zlatarev

Where is the Key Light Placed?

Key lights can be adjusted to be hard or soft, it all depends on your setup and how you want the end result to look like.

For the most used setup (three-point lighting) the key lights are adjusted at a 30-60 degree angle. 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 just above the eye line.

This is done to prevent any distortion to the subjects 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 subjects face is lit from below.

How Do You Use a Key Light?

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

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

Lighting a scene with only key light is insufficient, usually because your background will be left in the dark. To decrease contrast and add more illumination to the background, it is recommended to use fill lights. Fill lights will add more details lying in the background.

You can also reflect the already existing light on the surroundings as an alternative for fill lights. Reflecting light will make it appear much softer, thus decreasing the contrast.

Key light can also be passed through screens, filters, or even reflectors. Even the lights that pass through objects and obstacles will add more interesting visuals to the shot.

Key lights can also be colored, they don’t have to be full white anyways. Correct usage of colored keys will add more emotional depth towards a scene, compared to the usual full white key.

Color temperatures are also added to the mix. Natural lighting has different warmth depending on the sun and moon. Sunlight appears as a warmer white, while the moon has a much cooler white.

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 2:1. Meaning that your key light should be at least twice the brightness of your fill light. This ratio gives you a 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 doesn’t give off any dimensional benefits. Try using a 1.5:1 ratio for your videos that are intended to be inviting.

Fill light intensity should be throttled around the 50-75% mark. Marketing and commercial photographers will usually use a much higher intensity (85% and above) for a more even appearance.

key light brightness
Photo by Gordon Cowie

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 is used to decrease 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 source of illumination. It comes from the smart side of the subject and sets the atmosphere of a shot before it’s affected by everything else.

So from the get-go, both of these lights have different purposes. Now let’s move on to the usage of both of them in ratios.

When setting the light intensity, the key light is prioritized than the fill lights. Since fill lights hold a more supplementary role, it is always used at a low intensity and is usually half of the intensity of key lights.

The fill light is also used in various ways different from your key lights. Fill lights will often use modifiers that are portable to affect the lights, either making it softer or harsher.

It becomes possible for the photographer to make a warmer light by bouncing the flash to their hands, making the light softer by reflecting it on a wall, and many other methods.

Final Remarks

To sum up key light:

  • 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.
  • High-key lighting setup eliminates the shadow and contrast. It makes the scene appear more lighthearted and often used in a positive light. The key to fill ratio used is usually a 1:1 or 1.5:1.
  • Key light is used as the main source of illumination in three-point lighting. Commonly positioned at a 30-60 degree at an overhead height 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.
  • Basically, fill light reduces the amount of contrast and shadows (hence the name). On the contrary, the key light is the main source of light (also hence the name).

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.

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