Jan 299 min read

The Exposure Triangle

Updated: Feb 26

A Guide for Film Photography Beginners

If you are new to film photography, you may have heard of the term “exposure triangle” and wondered what it means. The exposure triangle is a concept that explains how three settings on your camera - aperture, shutter speed, and ISO - affect the exposure of your photos. Exposure is the amount of light that reaches the film when you take a picture. A well-exposed photo has a balanced amount of light and dark areas, with details and colours that are clear and pleasing to the eye. A poorly exposed photo can be too bright (overexposed) or too dark (underexposed), with details and colours that are lost or distorted.

In this article, we will explain how the exposure triangle works in beginner terms, and how you can use it to achieve the best exposure for your film photos. We will also cover some tips and tricks for shooting in different lighting situations, such as bright, low-contrast scenes and dark, high-contrast scenes. By the end of this article, you will have a better understanding of the exposure triangle and how to use it to improve your film photography skills.

Check out our guide to the "Sunny 16" rule for beginners.

What are the three parts of the exposure triangle?

The three parts of the exposure triangle are aperture, shutter speed, and ISO. Each of these settings controls how much light enters the camera and reaches the film. They also have other effects on the image quality, such as depth of field, motion blur, and graininess. Let’s look at each of these settings in more detail.

Aperture

Aperture is the size of the opening in the lens that lets light in. The aperture is measured in f-stops, such as f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, and f/16. The smaller the f-number, the larger the aperture, and vice versa. For example, f/1.4 is a very large aperture, while f/16 is a very small aperture.

The aperture affects the exposure by controlling how much light passes through the lens. A larger aperture lets in more light, while a smaller aperture lets in less light. For example, changing the aperture from f/4 to f/2.8 will double the amount of light, while changing it from f/4 to f/5.6 will halve the amount of light.

A picture of echinacea demonstrating narrow depth of field. — Shot with a wide open aperture, the echinacea in the foreground is in focus while the rest of the background falls off into a pleasing, swirly bokeh. Photo credit: Michael Elliott

The aperture also affects the depth of field, which is the range of distance in front of and behind the subject that appears in focus. A larger aperture creates a shallow depth of field, which blurs the background and foreground, while a smaller aperture creates a deep depth of field, which keeps everything in focus. For example, if you want to isolate your subject from the background, you can use a large aperture, such as f/2.8. If you want to capture everything in sharp detail, you can use a small aperture, such as f/11.

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Shutter Speed

Shutter speed is the length of time the shutter stays open to expose the film or sensor to light. It is measured in seconds or fractions of a second, such as 1s, 1/2s, 1/4s, 1/8s, 1/15s, 1/30s, 1/60s, 1/125s, 1/250s, 1/500s, and 1/1000s. The longer the shutter speed, the more light enters the camera, and vice versa. For example, a shutter speed of 1/2s will let in four times more light than a shutter speed of 1/8s.

The shutter speed affects the exposure by controlling how long the film or sensor is exposed to light. A longer shutter speed will brighten the image, while a shorter shutter speed will darken the image. For example, changing the shutter speed from 1/60s to 1/30s will double the amount of light, while changing it from 1/60s to 1/125s will halve the amount of light.

The shutter speed also affects the motion blur, which is the amount of movement that is captured in the image. A longer shutter speed will create more motion blur, while a shorter shutter speed will freeze the motion. For example, if you want to capture a moving subject, such as a car or a person, you can use a short shutter speed, such as 1/500s. If you want to create a sense of movement or show the passage of time, you can use a long shutter speed, such as 1/2s.

A black and white photograph of a couple in St. Pancras International, walking toward the camera, demonstrating slower shutter speed. — A slightly extended shutter speed to compensate for the poor, indoor lighting, caused this wonderful contrast of the bustling commuters in the foreground around the ambling elderly couple in the mid-ground. Photo credit: Michael Elliott

ISO

ISO is the sensitivity of the film to light. It is measured in ISO values, such as 50, 100, 200, 400, 800, 1600, 3200. The higher the ISO value, the more sensitive the film or sensor is, and vice versa. For example, ISO 100 is a low sensitivity, while ISO 1600 is a high sensitivity.

A black and white photograph of a flower still life, on slow film, demonstrating extreme fine grain. — A still life shot on Agfa Ortho 25 film - an slow, incredibly fine grained, high contrast film. Grain is virtually non-existent. I could use this film as my camera was set up on a tripod with a cable release. Photo credit: Michael Elliott

The ISO affects the exposure by controlling how much light is needed to create a well-exposed image. A higher ISO film requires less light, while a lower ISO film requires more light. For example, using a 200 speed film in place of a 100 speed film will halve the amount of light needed, while using a 50 speed film instead of a 100 speed film will double the amount of light needed.

The ISO also affects the graininess, which is the amount of random specks that appear in the image. A higher ISO film will result in more grain, while a lower ISO film will create less grain. For example, if you want to achieve a smooth and clean image, you can use a low ISO film, such as 100. If you want to add some texture and character to your image, you can use a high ISO film, such as 3200.

A black and white photo of a boat in a dry dock shot on high speed film demonstrating high graininess. — Fuji Neopan 1600 developed in a highly compensating, grain softening developer (D-23 1+3) still demonstrates huge gobs of grain throughout. Incredibly sharp, but incredibly grainy. Photo credit: Michael Elliott

Need a film camera? Don't know which one to buy? Check out our guide to the top 10 beginner film cameras you can get.

How do I use the exposure triangle?

Now that you know what the three parts of the exposure triangle are and how they affect the exposure and image quality, how do you use them to take better photos? The key is to find the right balance between the aperture, shutter speed, and ISO that will give you the desired exposure and creative effect. There is no one correct way to do this, as different situations and preferences may require different settings. However, here are some general steps and tips that can help you use the exposure triangle effectively.

Step 1: Choose your priority

The first step is to decide what is the most important aspect of your image that you want to control. Is it the depth of field, the motion blur, or the graininess? Depending on your answer, you will choose one of the three settings as your priority and adjust it accordingly. For example, if you want to control the depth of field, you will choose the aperture as your priority and set it to the desired f-stop. If you want to control the motion blur, you will choose the shutter speed as your priority and set it to the desired value. If you want to control the graininess, you will choose the ISO as your priority and use the correct speed film for the situation.

Since you cannot (viably) adjust the film speed in the middle of a roll, you should always pick your film carefully, balancing the lighting situations you expect to experience with the amount of grain you consider acceptable.

Step 2: Adjust the other setting

The second step is to adjust the other setting to balance the exposure and achieve the correct amount of light. Remember, changing one setting will affect the exposure, so you need to compensate with the other setting. For example, if you choose the aperture as your priority and set it to a large value, such as f/2.8, you will let in more light and overexpose the image. To balance the exposure, you need to increase the shutter speed. If you choose the shutter speed as your priority and set it to a short value, such as 1/500s, you will let in less light and underexpose the image. To balance the exposure, you need to set the aperture to a larger value (open up the lens).

In film photography, we don't have the luxury of changing the film's speed while shooting a roll - unlike in digital where the ISO (i.e. the gain of the sensor - the equivalent to film ISO) can be changed on the fly. That's why it's important to consider the need for balancing the amount of grain with the lighting conditions likely to be encountered prior to loading your film!

Step 3: Check the exposure

The third step is to check the exposure using the camera’s light meter or a handheld meter, or a phone app. Evaluate the exposure to see if you are over or under exposing, or if you've got it just right.

What are some tips and tricks for different lighting situations?

One of the challenges of film photography is that you cannot change the ISO of the film once you load it into the camera. This means that you have to choose the right film for the right lighting situation, or use filters and flash to modify the light. Here are some tips and tricks for shooting in different lighting situations with film.

Bright, low-contrast scenes

Bright, low-contrast scenes are those that have a lot of light and little difference between the light and dark areas, such as a sunny day with clear sky, a snowy landscape, or a white wall. These scenes can be tricky to expose correctly, as the camera’s light meter may be fooled by the brightness and underexpose the image, making it look dull and gray. To avoid this, you can use the following techniques:

Underexpose and push process. Pushing increases contrast as the highlights develop quicker and the shadows develop more slowly. You need to underexpose to make sure that you don't blow out the highlights in development.
Use a lower ISO film, such as 100 or 200, to reduce the sensitivity and avoid overexposure.
Use a smaller aperture, such as f/11 or f/16, to limit the amount of light entering the camera and increase the depth of field.
Use a faster shutter speed, such as 1/250 or 1/500, to shorten the exposure time and freeze any motion in the scene.
Use an exposure compensation dial, if your camera has one, to adjust the exposure by +1 or +2 stops, to make the image brighter and more vivid.
Use a polarizing filter, if you have one, to reduce glare and reflections, enhance contrast, and deepen the colours of the sky and water.

Dark, high-contrast scenes

These are scenes that have a lot of difference between the light and dark areas, such as a night scene with street lights, a sunset or sunrise, or a silhouette. These scenes can be challenging to expose correctly, as the camera’s light meter may be confused by the contrast and overexpose or underexpose the image, making it lose details and colors. To avoid this, you can use the following techniques:

Overexpose and pull process. Pulling reduces contrast as the highlights are given less of a chance to develop versus the shadows. To ensure that enough shadow detail is captured, you must overexpose.
Use a higher ISO film, such as 400 or 800, to increase the sensitivity and capture more details in the shadows.
Use a larger aperture, such as f/2.8 or f/4, to let in more light and create a shallow depth of field, which can isolate your subject from the background and emphasize the contrast.
Use a slower shutter speed, such as 1/30s or 1/15s, to allow more light to reach the film or sensor, but be careful not to introduce camera shake or motion blur. You can use a tripod or a flash to stabilize the image.
Use spot metering or exposure compensation to adjust the exposure based on the most important part of the scene, such as the subject’s face, the sky, or the light source. You can also use bracketing to take multiple shots with different exposures and choose the best one later.

Exposure triangle cheat sheet

A cheat sheet is a handy tool that can help you remember the relationship between the aperture, shutter speed, and ISO, and how they affect the exposure and image quality. You can create your own cheat sheet or download one from the internet, such as this one.

An exposure triangle cheet sheet. — WClarke and Samsara, CC BY-SA 4.0, via Wikimedia Commons

A cheat sheet usually shows the values of the three settings for different lighting situations, such as sunny, cloudy, indoor, etc. It also shows the effects of changing the settings, such as increasing or decreasing the depth of field, motion blur, or graininess. You can use a cheat sheet as a guide, but you should also experiment with different settings and see the results for yourself.

The exposure triangle is a concept that explains how the aperture, shutter speed, and ISO work together to control the exposure and image quality of your film photos. By understanding the exposure triangle and how to use it, you can take better photos in different lighting situations and achieve the creative effects that you want. Remember, there is no one correct way to set the exposure triangle, as different situations and preferences may require different settings. The best way to learn is to experiment and have fun with your film camera.

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