The Exposure Triangle
What is the Exposure Triangle?
The exposure triangle consists of three key elements: aperture, shutter speed, and ISO. These three settings work together to determine the exposure of your photograph. Adjusting one element will often require compensating with another to maintain the correct exposure.
Aperture
Aperture refers to the size of the opening in your camera lens that allows light to enter. It is measured in f-stops (e.g., f/2.8, f/4, f/5.6). A lower f-stop number means a larger aperture, which lets in more light, while a higher f-stop number means a smaller aperture, letting in less light.
Wide Aperture (Low f-stop): More light enters, creating a shallow depth of field. This is great for portraits where you want a blurred background.
Narrow Aperture (High f-stop): Less light enters, creating a deep depth of field. This is ideal for landscapes where you want everything in focus.
Shutter Speed
Shutter speed is the amount of time the camera’s shutter is open, allowing light to hit the sensor. It is measured in seconds or fractions of a second (e.g., 1/1000s, 1/250s, 1s).
Fast Shutter Speed: Freezes motion, perfect for action shots or sports photography.
Slow Shutter Speed: Captures motion blur, ideal for creative effects like light trails or smooth water in landscape photography.
ISO
ISO measures the sensitivity of your camera’s sensor to light. A lower ISO value (e.g., 100) means less sensitivity, resulting in finer grain and less noise. A higher ISO value (e.g., 1600) increases sensitivity, useful in low-light conditions but can introduce more noise.
Low ISO: Best for bright conditions or when you want the highest image quality.
High ISO: Useful in low-light situations but can result in grainier images.
Balancing the Triangle
To achieve the perfect exposure, you need to balance all three elements of the exposure triangle. Here’s how they interact:
Increase Aperture (Lower f-stop): More light enters, so you might need a faster shutter speed or lower ISO to avoid overexposure.
Decrease Shutter Speed: More light enters, so you might need a smaller aperture (higher f-stop) or lower ISO.
Increase ISO: More sensitivity to light, so you might need a faster shutter speed or smaller aperture to avoid overexposure.
Here's a practical example using the Sunny 16 Rule. By the way, see this article on "What Is The Sunny 16 Rule?" for more details, but as a recap, the Sunny 16 rule states that on a sunny day, you can set your aperture to f/16 and your shutter speed to the inverse of your ISO for a correct exposure. For example, if your ISO is 100, your shutter speed should be 1/100 second.
Example Settings:
Here are some combinations of settings that would give you the same exposure using the Sunny 16 rule:
Sunny 16 Rule Settings:
Aperture: f/16
Shutter Speed: 1/100 second
ISO: 100
Alternative Settings for the Same Exposure:
Aperture: f/11
Shutter Speed: 1/200 second
ISO: 100
Here, opening the aperture by one stop (from f/16 to f/11) allows twice as much light in, so you need to double the shutter speed (from 1/100 to 1/200) to maintain the same exposure.
Another Alternative:
Aperture: f/8
Shutter Speed: 1/400 second
ISO: 100
In this case, opening the aperture by two stops (from f/16 to f/8) allows four times as much light in, so you need to quadruple the shutter speed (from 1/100 to 1/400) to maintain the same exposure.
Using Higher ISO:
Aperture: f/16
Shutter Speed: 1/400 second
ISO: 400
Here, increasing the ISO by two stops (from 100 to 400) makes the sensor more sensitive to light, so you need to increase the shutter speed by two stops (from 1/100 to 1/400) to maintain the same exposure.
Hopefully you can see from those examples that changing one setting means a change to another setting, but as long as you adjust each by the same proportion (known as "stops") then you'll still balance out your expousures. Click this link, "What Are Stops in Photography" for more on this, but super duper quickly, a “stop” is a unit of measurement in photography that represents a doubling or halving of the amount of light that reaches the camera sensor. Adjusting any of the three elements of the exposure triangle (aperture, shutter speed, ISO) by one stop will either double or halve the exposure.
Practical Tips for Beginners
Start with Aperture Priority Mode: This mode allows you to set the aperture while the camera adjusts the shutter speed. It’s a great way to learn how aperture affects your photos.
Experiment with Shutter Speed: Try different shutter speeds to see how they affect motion in your images.
Adjust ISO as Needed: Keep ISO as low as possible for the best image quality, but don’t be afraid to increase it in low-light situations, or to use a faster film.
Conclusion
Mastering the exposure triangle is a crucial step in your photography journey. By understanding how aperture, shutter speed, and ISO work together, you can take control of your camera and create beautifully exposed images. So grab your camera, experiment with these settings, and watch your photography skills grow!