Lighting ratios

Balance brilliance and master your lighting ratios for striking images...

What is a lighting ratio?

The lighting ratio compares the key light (the main light source), and the fill light. This ratio helps determine the contrast in the image by showing the difference between the lightest and darkest parts of the subject.

When understanding the concept of lighting ratios, I've found it's best to break it down into the three key areas of focus:

1. The key light
2. The fill light
3. F-stops (aperture)

In order to understand lighting ratios, you need to have an understanding of these three concepts. Let's take a brief look at each concept, and then I'll break each concept down into it's own section.

With key light being the main source of where the shadows fall, the fill light will then "fill" in the shadows. When both of these light sources are used, a softer light will be created on the subject.

• A higher lighting ratio will make your image more contrasting.
• A lower lighting ratio will lower the contrast.

The ratio is based on the brightest part of your subject to the least bright parts.

Light is measured in foot candles.^[1] Say the key light is 100-foot candles while the fill light is at 100-foot candles, the ratio will be 1:1. If the key light is at 200-foot candles and the fill light is 100-foot candles, the ratio will then become 2:1.

Here is a side-by-side comparison showing when only a key light is used and when a key light + fill light are used. This is a simple example showing the difference between higher and lower lighting ratio. On the left image, when only using a key light, you will notice a higher lighting ratio and more contrast. On the right, when using a key light and fill light together there will be a lower lighting ratio and less contrast:

Light can be measured in stops, with each increase doubling the brightness and each decrease halving it. Adjusting stops can be achieved by modifying the exposure triangle or changing the distance and intensity of the light sources.

The Exposure Triangle:

• Aperture: This setting will affect your depth of field and is measured in f-stops. If you use a large aperture (smaller f-stop number like f/1.8), the depth of field becomes shallower, and the camera can absorb more light. The reverse applies if you are using a smaller aperture (higher f-stop number like f/16).
• Shutter Speed: Essentially, it’s the time your shutter can open and close. A faster shutter speed allows you to "freeze" moving objects, saving you from the usual blur when capturing a moving object. Since a fast shutter speed closes so fast, it doesn’t allow much light to enter. A slow shutter speed is more vulnerable to motion blur and camera shake but lets in more light.
• ISO: This setting simply brightens your photo. Most cameras nowadays can shoot using 3200 ISO before emitting visually unflattering noise.^[2] ISO helps you by providing flexibility in changing your aperture and shutter speed.

How does the key light affect lighting ratios?

By definition, the key light is your brightest light source. As the main source of light, it controls the ratio and the amount of light/shadow intensity.

The key light is oftentimes used in the three-point lighting method, accompanied by the fill light and backlight/hair light. Photographers can place their main lights wherever they please in the studio. The main purpose of your key light is to illuminate the subject, provide highlights towards the form, and, lastly, the dimension of the subject.

An image can still be taken without a key light. The result is a silhouette effect that looks pretty cool and edgy and reminds me of James Bond.

High-key lighting

High-key lighting will reduce the scene’s lighting ratio. This translates into less contrast between the bright and dark areas and uses lighting ratios such as 1:1 or 2:1.

Less contrast between both elements creates an upbeat mood, which is often followed by a positive message. You’ll often witness this type of lighting in video interviews, educational videos, training videos, and many more.

To produce this message loud and clear, your content and lighting must work hand in hand. If you deliver a negative message using high-key lighting, your audience might capture a confusing message. But this is not a restriction on your creativity and serves as a rule of thumb. As a fellow photographer, I encourage you to experiment and enjoy it.

Low-key lighting

Low-key lighting also gives you the least amount of mid-tones and whites and uses lighting ratios such as 8:1 and going up to 16:1 or even higher. Photographers have been using this technique to create a more dramatic and mysterious mood for the image.

The lighting technique creates a moody dark tone with a hint of seriousness and mystery, which naturally looks better in black and white. Film noir and crime dramas just love using low-key lighting; their themes thrive in the high contrast lighting.

You will barely see low-key lighting in advertisements or promotional material due to its ambiance. Even if you see one, it will most likely tip to the more emotional and gloomy side.

How does fill light affect lighting ratios?

Fill lighting serves a more complementary role if compared to the key light and backlight.

Fill light basically fills in the shadows that are created by the key light. The strength of the fill light will never be over the key light; at most, it’ll be on par with the key light.

As a light that is mainly used to fill the shadows, photographers don’t really use too much fill. To maintain a sense of drama, they use a lot of key light and minimum fill light. For scenes that need to look more upbeat and positive, they’ll use a fill light with the same strength as the key light.

And one thing to note — you don't have to use studio lights as a fill light. As you'll see in the later sections, I used a studio light as my key light and sunlight coming through a window as my fill light.

Now that we have a better understanding of the key light and fill light, let's take a look at f-stops and their role in understanding lighting ratios. To better understand how f-stops relate to the lighting ratio and how to calculate them, here’s an explanation followed by an f-stop chart.

How do f-stops affect and lighting ratios?

F-stops are used to measure the intensity of light. Each change in an f-stop represents a doubling or halving of the amount of light entering the camera. When measuring your key light and fill light with a light meter, the difference in their f-stop readings determines your lighting ratio.

Here are a couple examples:

• If your key light reads f/8 and your fill light reads f/5.6, there is a 1-stop difference. This difference means the key light is twice as bright as the fill light, resulting in a 2:1 lighting ratio.
• If the key light reads f/8 and the fill light reads f/4, there is a 2-stop difference. This translates to a 4:1 lighting ratio because each stop doubles the light (2^2 = 4).

Here is the f-stop chart so you can get a better visual. To read the chart, start at the first column (F-Stop) then read it left to right, seeing how a change to the next f-stop down (wider aperture - more light) would affect light intensity, and how a change to next f-stop up (narrower aperture - less light) would affect light intensity.

For example, looking at the third row (reading left to right), starting at an f-stop of f/2.0, a change to the next f-stop down (wider aperture) would be f/1.4 which would affect the light intensity by making it 2x brighter. If we instead did a change to the next f-stop up (narrower aperture), it would be f/2.8 which would affect the light intensity by making it half as bright:

To better understand this f-stop chart, remember that each f-stop change represents a doubling (+1 stop) or halving (-1 stop) of light intensity. For example, going from f/1.4 to f/2.0 would be a halving of light (-1 stop) and going from f/2.0 to f/1.4 would be a doubling of light (+1 stop).

When determining the lighting ratio, count the number of f-stop differences between the key and fill light readings. Let's look at some examples and use the chart for reference:

1-Stop Difference: 2:1 Lighting Ratio

• Example: The key light reads f/8, and the fill light reads f/5.6.

A 1-stop difference (f/8.0 → f/5.6) means the key light is twice as bright as the fill light, resulting in a 2:1 lighting ratio. This ratio provides a subtle contrast and is often used for soft portrait lighting.

And it could seem a little counterintuitive, so although f/8.0 is a narrower aperture and lets in less light, it is used to measure the light output itself. The fill light at f/5.6 (a wider aperture) allows more light to hit the sensor and indicates that if your key light reads f/8.0 on a light meter and the fill light reads f/5.6, the key light is twice as intense as the fill light. This creates a 2:1 lighting ratio.

So remember this and let's look at the next two.

2-Stop Difference: 4:1 Lighting Ratio

• Example: The key light reads f/8, and the fill light reads f/4.

A 2-stop difference (f/8.0 → f/5.6 → f/4.0) means the key light is four times as bright as the fill light, resulting in a 4:1 lighting ratio. This ratio creates more defined shadows and highlights and is used for a stronger sense of depth in portraits or dramatic scenes.

3-Stop Difference: 8:1 Lighting Ratio

• Example: The key light reads f/8, and the fill light reads f/2.8.

A 3-stop difference (f/8.0 → f/5.6 → f/4.0 → f/2.8) means the key light is eight times as bright as the fill light, resulting in an 8:1 lighting ratio. This high-contrast ratio is ideal for dramatic, moody lighting where shadows are pronounced, such as in low-key photography.

With these factors in mind, let's explore common lighting ratios and their effects on images.

What are the common lighting ratios?

Common lighting ratios will always differ depending on the situation you’re in and the client’s request.

But I assume you’re referring to the lighting ratio for portraits inside a studio. Lighting ratios in a studio can vary depending on the agreement between the client or personal tastes. Generally, professional photographers will aim for a realistic, flattering, and three-dimensional image.

Firstly, they prioritize separating the subject from the background. Nowadays, it becomes too easy to introduce too much light onto your subject and erase all of the subject’s shadows.

1:1 Lighting ratio

The basic ratio is the 1:1 lighting ratio. This ratio provides an evenly lit subject from both sides; it doesn’t have any noticeable shadows and sometimes makes the image rather flat.

The subjects still look great, and the light is still flattering, yet it feels incomplete. Generally, fashion and beauty photographers will use this ratio to make their subjects look flawless (no wrinkles, acne, pores, etc.).

2:1 Lighting ratio

Then, there is the 2:1 lighting ratio, with a one-stop difference from the highlight to the shadow. The light is enough to add a dimension to the image. Yet the light is soft, creating the perfect ambiance for child photography. It makes the image feel a bit innocent and pure.

4:1 Lighting ratio

With a two-stop difference between the lights and shadows, there’s a 4:1 lighting ratio. This is the most commonly used light ratio for portraits.

It serves as an all-around light ratio that can be used in most types of photos. A decent amount of shadow makes the image livelier than the 1:1 ratio.

8:1 Lighting ratio

The 8:1 lighting ratio with a 3-stop difference produces an almost perfect amount of light and shadow on your subject.

With this ratio, your image becomes more dramatic and much more flattering for your subject. That is all! The four ratios mentioned above are the most commonly used in portrait photography. Of course, everyone has their own preferences and style when it comes to photography.

16:1 Lighting ratio

Lastly, the 16:1 lighting ratio with a 4-stop difference produces an intense contrast between light and shadow on your subject. This high-contrast ratio is often used for creating dramatic and moody images where deep shadows play a significant role in shaping the scene.

With a 16:1 ratio, the key light is 16 times brighter than the fill light, resulting in strong highlights and deep shadows that add depth and drama to the subject. This lighting setup is ideal for artistic portraits or scenes where a sense of mystery or power is needed. It accentuates facial contours and textures, making the subject stand out with bold, striking light and shadow interplay.

This ratio is less common in standard portrait photography due to its high contrast but can be used creatively in other types of portraits to evoke strong emotions or emphasize specific features. That is all! The ratios mentioned above, including 2:1, 4:1, 8:1, and 16:1, provide a range of options for portrait photography, but each photographer may have their own preferences and style.

Feel free to explore and experiment with the various light ratios and equipment to see which works best. There are tons of lighting ratio charts available online to download and print, which can help you decide the ratio you want for a certain image.

The more you get used to your lighting ratio, the faster you’ll recognize the most appropriate ratio.

How to choose the best lighting ratio?

Here's a step-by-step guide to help you choose the best lighting ratio:

1. Understand lighting ratios

To choose the best lighting ratio for your situation, you first need to understand the different lighting ratios and their effects. Common ratios include 1:1 (even lighting), 2:1 (subtle shadows), and higher ratios like 4:1 or 8:1 (strong shadows).

2. Determine your subject

The second step is to determine your subject. Consider what you are photographing and the desired outcome. For portrait photography, lighting ratios can affect the mood, emphasis on facial features, and the overall look of the subject.

3. Identify the mood

Think about the mood you want to convey in the photograph. A low lighting ratio (more even lighting) can create a soft and flattering look, while a higher ratio (more contrast) can create a dramatic and edgy appearance.

4. Analyze facial features

Pay attention to the subject's facial features. A lower lighting ratio can help minimize imperfections and create a flattering look. A higher ratio might be appropriate for more defined features and a stronger contrast.

5. Consider the environment

Take into account the environment or setting of the photograph. Some scenes might benefit from a balanced lighting ratio to preserve details, while others could benefit from dramatic contrasts to add depth and dimension.

6. Experiment and test

Experiment with different lighting setups and ratios during your photoshoot. Take test shots with various ratios and review the results. This will help you see how the lighting impacts the final image and how it aligns with your vision.

7. Adjust for skin tone

If you're photographing people, consider their skin tone. Different skin tones react differently to lighting ratios. Ensure your chosen ratio enhances the subject's skin tone rather than causing unwanted color shifts or harsh shadows.

8. Don't be afraid to break rules

While guidelines are helpful, don't be afraid to break the rules and experiment creatively. Sometimes, unexpected lighting ratios can lead to unique and striking results.

9. Review and refine

Review the test shots and determine which lighting ratio best achieves your desired outcome. Pay attention to the balance between shadows and highlights, as well as the overall mood of the image.

10. Post-processing

Remember that you can also adjust the lighting ratio during post-processing using editing software. However, it's best to achieve the desired ratio as closely as possible during the initial photoshoot.

How do you calculate lighting ratios?

To calculate lighting ratios, it's an easy 5-step process.

1. Set up your lighting

The first step is to set up your lighting. You'll want to position your key light and fill light according to your desired lighting setup.

In this example, you can see I set up my Godox studio light to the left to be the key light, and I'm using the sun from the window on the right as the fill light.

2. Meter the key light

The second step is to place a light meter in front of your subject, pointing directly at the key light. You'll want to make sure you shield the meter from any other light sources.

Take a reading from the light meter and if you're using a strobe flash instead of a continuous light source like I'm using, you'll want to take a reading by triggering the key light (usually down by using a flash trigger or syncing with the meter).

In this example, I set my camera to ISO 800 with a shutter speed of 1/250s and aperture of f/2.8 for a blurred background. So to sync my camera settings with the light meter I input the same ISO and shutter speed into the light meter.

I wanted to capture a 4:1 lighting ratio so this means I need my key light to be 2-stops more narrow, so the key light can be four times as bright as the fill light. When I metered the key light I got f/2.8, which means I'll need my fill light to be f/1.4 (f/2.8 → f/2.0 → f/1.4).

3. Meter the fill light

Now that we've metered for the key light and received the value f/2.8, I'll need to meter for the fill light.

As mentioned, since I'm going for the 4:1 lighting ratio look, I'll need to meter for f/1.4 on the fill light to have a 2-stop difference. So in this case, I pointed the light meter towards the fill light now which is the window.

4. Calculate the lighting ratio

Once you have a key light and fill light value, it's time to calculate the key light and fill light readings.

As mentioned earlier, each stop difference represents a doubling or halving of light. So since we received f/2.8 on the key light, that means 1-stop down would be f/2.0, and then another 1-stop down would be f/1.4, equaling a total of 2-stops.

So we have a key light that is 4x brighter than the fill light. And as we covered earlier, a 2-stop difference means a 4:1 lighting ratio, success! We've achieved a 4:1 lighting ratio:

5. Adjust the lights as needed

The fifth step is to adjust the lights as needed.

If you calculate the lighting ratio and don't end up with your desired lighting ratio. Adjust the lighting power by bringing the light closer or further away, or adjusting the light power on your flash either higher or lower.

Keep making these adjustments and metering the results until you reach your desired lighting ratio!

What about the odd lighting ratios?

You may be wondering about the odd lighting ratios such as the 3:1, 5:1, 7:1, or 9:1 lighting ratios. Do they even exist?

Yes, odd lighting ratios like 3:1, 5:1, 7:1, or 9:1 do exist and can be used in photography, though they are less commonly referenced than the typical even ratios like 2:1, 4:1, 8:1, and 16:1. These odd ratios represent intermediate levels of contrast and can provide more nuanced control over the balance between light and shadow.

Essentially, lighting ratios atios like 2:1, 4:1, and 8:1 are often taught as benchmarks because they are simpler to calculate and use with stops of light (each stop represents a doubling or halving of light intensity).

While odd ratios provide more options, they may be less frequently used because many photographers prefer easy-to-remember increments that correspond to full-stop differences in light intensity.

What lighting ratio would virtually eliminate shadows?

If you’re talking about a fully illuminated face from each side, then it’s the 1:1 ratio.

It looks good in certain images, which makes them look more flattering and beautiful. But shadows actually play a larger role, and they’re not just a nuisance. Shadows appear when an object blocks the light source, making the object’s shape projected onto the shadow.

Using shadows will help direct the viewer’s attention toward a specific location. It reveals features that may be better off unseen. They add drama, emotion, and mystery to the photo.

In conclusion, the lighting ratio is the ratio of key light to fill light. The 1:1 ratios (with virtually no shadows), 2:1, 4:1, and 8:1 ratios (with the most shadows) are commonly used.

However, each ratio has its own uses and ambiance, depending on the key light and fill light. The key light is your main (brightest) light, while the fill light "fills" in the shadows. Knowing when to use certain ratios may be hard at first, so consider using a lighting ratio at first. The more you practice and use lighting ratios in your photo shoots, the faster you’ll get accustomed to it. Have fun and good luck!