Photography and cinematography are often referred to as “painting with light.” This means that photographers and videographers need to have a keen understanding of how to use light when capturing images, from both an artistic and scientific standpoint. Lighting ratios stand firmly in between the two camps, used creatively but achieved through a mathematical formula. Let’s look at what a lighting ratio is, and how you can use it.
What is lighting contrast?
Understanding lighting ratio
Lighting ratios are fundamental to photography, and yet many photographers don’t have a firm grasp on the term until years into their craft. Instead, they use the idea of lighting ratio without having the label for it. So let’s define that label.
LIGHTING RATIO DEFINITION
What is a lighting ratio?
A lighting ratio refers to the difference in intensity between the light sources on a subject, primarily the key and the fill. The higher the lighting ratio, the higher the contrast of an image.
The American Society of Cinematographers outline the calculation of a lighting ratio as (key light + fill light) : fill light. Typically, the fill light is set at one, so that lighting ratios are 1:1, 2:1, 4:1, etc..
Lighting Ratio Uses:
- Deciding exposure
- Establishing mood
- Maintaining continuity
Now that we know what a lighting ratio is, let’s look at why it is so foundational to photography and cinematography.
Why lighting ratios are important
Why use lighting ratios?
There are a few reasons you’ll want to be familiar with light ratios as a photographer or cinematographer. The first is that it helps you expose an image. If you know your lighting ratios, you’ll know what to expect when you expose an 8:1 ratio rather than a 2:1 ratio.
Lighting ratios are crucial to establishing the tone of an image. A high ratio like 10:1 will be very moody and even foreboding. A lower ratio, like 2:1, will feel a lot softer.
Say you’re filming a comedy. You’re looking to establish a fun and whimsical tone. This means you’ll likely want to keep your lighting ratio pretty low.
Once you decide on a desired level of contrast, lighting ratios can help you maintain continuity. If you’re shooting a conversation with a simple shot reverse shot set up, you’ll probably want the lighting to be similar on both characters, since they’re in the same space. You can quickly ensure that you’re doing that by measuring the lighting ratio on one shot, and achieving the same ratio on the next.
Contrast lighting equation explained
How to measure lighting ratios
Knowing what a lighting ratio is all well and good, but you’ll also need to know how to measure it. It’s a bit more complicated than guessing based on how harsh a shadow is.
As we stated, a lighting ratio is simply the comparison between the brightness of the key light (your main light source) and the fill light (which softens shadows). So measuring a lighting ratio means measuring the strength of each light.
To measure lighting ratios accurately, you’ll need a light meter, either a handheld device or a built-in meter in your camera. First, identify your key light and fill light. Set your subject and lights in position, then follow these steps:
- Measure the light falling on the key light side of your subject’s face using the incident mode on your meter (this mode measures the light hitting the subject, not what’s reflected). Record the reading in f-stops or foot candles.
- Take the same measurement on the other side of the subject’s face (where the fill light is hitting). Record this reading as well.
- Compare the values. If the key light reads f/8 and the fill light reads f/4, you’re working with a 4:1 lighting ratio. That’s because each f-stop represents a doubling or halving of light. So f/8 is two stops brighter than f/4.
One stop difference = 2:1 ratio
Two stops difference = 4:1 ratio
Three stops = 8:1 ratio
If you don’t have a light meter, you can estimate ratios by checking histogram data or using your camera’s spot meter to read different sides of the face. You can also use tools like waveform monitors or false color overlays to help you judge exposure differences between lit and shadowed areas.
Let’s take a peek at how these ratios actually look on a subject.
Contrast lighting examples
Different lighting ratios
As we’ve said, lighting ratios can drastically alter the mood and atmosphere of an image. Here’s an overview of the most commonly used ratios.
A 1:1 lighting ratio means that the key light and the fill light are at equal intensity. This creates an evenly lit image with almost no visible shadows and very little contrast. In a portrait, the evenness ensures that facial features are clearly defined without dramatic shadows. Keep in mind, though, that this flat lighting can sometimes lack visual interest or depth.
With a 2:1 lighting ratio, the key light is twice as bright as the fill light. This adds moderate contrast to the image, enhancing the sense of depth and helping certain details stand out. This ratio strikes a balance between realism and drama. The shadows become more defined, but not really harsh.
A 4:1 lighting ratio raises the contrast significantly, with the key light being four times brighter than the fill. This setup generates stronger shadows and more striking highlights. It’s a common choice for fashion photography or dramatic scenes in film. The look is expressive, though keep in mind it may start to obscure some facial features, depending on placement.
An 8:1 lighting ratio gives you a highly dramatic and stylized visual, with a bold contrast between illuminated and shadowed areas. This ratio can often be found in black and white photography or film genres like noir and horror. Because it can obscure details and create a stark mood, it's best used selectively and with a clear creative intent.
Each ratio offers a different storytelling tool, and understanding them allows photographers and filmmakers to sculpt light with precision and purpose.
Up Next
The ultimate guide to film lighting
Lighting ratios are just scratching the surface of the art and science of lighting. If you’re starting out as a cinematographer, there’s a whole range of lighting terms and techniques you should know– and we’ve assembled them in one place.
Film lighting guide →
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