What Is Fill Light, and How Can It Help Your Lighting Design? 

Highlights – Your fill light works in tandem with your key light to lift shadows and highlight details in your scene. The intensity of the fill light is usually about half that of the intensity of the key light. A fill light does not have to be an actual light; often, a reflector will suffice.

Every scene has a main or key light, but your key light will often benefit from the addition of a fill light as well. Fill lighting is used to lift the shadows cast by the key light, draw attention to details, and add dynamism to a shot. 

Consider the fill light to be your key light’s right-hand man; they work as a team, similar to Sherlock Holmes and Dr. Watson or Xena and Gabrielle. Knowing how to use fill light effectively can make a huge difference in the look and feel of your films.

A fill light allows you to control the contrast, brightness, depth of shadows, and dimension of a scene. It’s not so much a question of key light vs. fill light as it is of key light and fill light.

What Is Fill Light, and How Can It Help Your Lighting Design?

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What exactly is a fill light? 

When using a 3-point lighting setup, your key light is your main light, which is typically positioned between 30 and 45 degrees camera-left or camera-right. Your fill light will be positioned at roughly the same angle as the key light but on the opposite side of the camera. 

The backlight (also known as a hair light or rim light) is the third light in the 3-point lighting setup, and it helps separate the subject from the background and add depth to the scene.

The fill light will not be as bright as your key light, but how bright you want it depends on the type of lighting you want for your scene. It doesn’t even have to be a light. We’ll return to both of these topics later. 

Fill lights, on the other hand, aren’t limited to 3-point lighting setups. If you’re shooting in natural light, you may need to lift the shadows, especially if you’re using the sun for backlighting and don’t want a silhouette. If you’re using overhead lighting, a fill light from below can help to eliminate dark shadows under your subject’s eyes, nose, and chin.

A fill light is used anywhere you need to light the shadows cast by your key light.

What is the purpose of a fill light? 

Film Lighting

There are four major areas where a fill light can help your scene: 

  1. Calculating the contrast ratio in your shot (the difference between the lightest and darkest areas of your shot)
  2. Adding dimension and depth 
  3. Creating a more even lighting pattern 
  4. Bringing out a subject’s details and shapes

How to Use a Fill Light in a Variety of Lighting Setups

Your fill light is secondary to your key light when creating a YouTube lighting setup or something for a commercial or documentary. As a result, it should be counteracting the shadows cast by your key light rather than casting its own. To accomplish this, three factors must be considered when deploying your fill light. 

  • The first is its location. The key light should be balanced. 
  • Then there’s the issue of quality. A fill light usually produces soft, diffuse light in order to avoid casting its own shadows. If the shadows are too distinct and compete with those from the key light, you can use a diffuser to help achieve this.
  • Finally, take into account the intensity of the light from your fill light. The fill light ratio, also known as the key/fill ratio, is the relationship between the quantity of light from the key light and the quantity of light from the fill light. The key light will always be stronger than the fill light, but using more fill light will result in a brighter, more softly lit shot. When you use less fill light, your shot will have more contrast and defined shadows.

A ratio of 2:1 is a good place to start, with the key light being twice as bright as the fill light. This results in a softer lighting effect with few shadows and little contrast. 

You’ll want a lower fill ratio for a high-key lighting effect that looks optimistic, upbeat, and airy, but start with 2:1 and see how it looks. The fill light, once again, should not be brighter than the key light. 

If you want a darker, moodier low-key look, reduce the intensity of the fill light by a factor of 8 or so. The ratio of your fill light to your key light will determine the look and feel of your film.

Different kinds of fill lights

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Lighting fixtures 

Another light, less intense than your key light, is probably the first light that comes to mind when you think of fill light in a video (or in photography). For example, if you use a softbox or umbrella as your key light, you can use a second, lower-intensity light as your fill light. 

While you may think of a ring light as a key light, it can also be used effectively as a fill light. If you want to give your fill light a more natural feel, try using a practical, which could be anything from a desk lamp to a tablet or mobile phone.

reflector bounce light why

Bounce cards and reflectors 

As previously stated, your fill light does not have to be provided by a lighting unit. Reflectors and bounce boards are great for fill lighting. If you’re shooting with natural light and don’t have access to a lighting unit, a reflector can help fill in the shadows in a sunny scene. 

They are not, however, limited to on-location shoots. They can be used in a studio or on a set, especially if a strong light source is not required. A reflector can bring out detail in a scene without sacrificing contrast.


White or pale-colored walls will softly reflect light back onto your scene from your key light. It’s a great way to make the most of your set, but make sure your subjects know exactly where they need to be so that light falls on them accurately to lift the shadows the way you want it.

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Filling in the gaps 

Negative fill lighting, also known as neg fill, is the polar opposite of a reflector. It’s a black flag or piece of fabric that you use to prevent light from entering your scene and maintain a higher level of contrast.

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One of the most important tools in your filmmaking arsenal is your fill light.

It only takes a few adjustments to change the look and feel of your work, and it doesn’t even have to be a lighting unit. So grab a reflector and see how much definition a fill light can add to your films.

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About the author: Trent (IMDB Youtubehas spent 10+ years working on an assortment of film and television projects. He writes about his experiences to help (and amuse) others. If he’s not working, he’s either traveling, reading or writing about travel/film, or planning travel/film projects.

What Is Fill Light, and How Can It Help Your Lighting Design?

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