Unit 3: Photography Basics
How do aperture, shutter speed, and ISO play together?
Introduction to the Exposure Triangle
The exposure triangle is a term you'll hear often in photography circles—and for good reason. Understanding it is a helpful way to start understanding how to take full control of your photos. But what exactly is it?
The exposure triangle is a fundamental concept that describes the relationship between three essential settings: aperture, shutter speed, and ISO. These three elements work together to determine how much light reaches your camera sensor, directly affecting the brightness and quality of your image.
A visual representation of the Exposure Triangle. Download a high-resolution version here.Camera Settings
Your exposure depends on the three settings that make up the exposure triangle. We'll cover each one in detail later in this unit, but here’s a quick introduction:
Shutter Speed
The shutter is like a fast-moving curtain inside your camera that opens and closes to control how long light reaches the sensor. Shutter speed is simply the amount of time this curtain stays open. A faster shutter speed lets in less light, while a slower shutter speed allows more light to hit the sensor.
Shutter speed also affects how motion appears in your images. A fast shutter speed freezes motion, while a slower one introduces motion blur—we'll explore this more later in this lesson.
Aperture
As we covered in the gear unit, aperture is the adjustable opening in your lens that controls how much light enters before hitting the sensor. A wider aperture lets in more light, while a narrower aperture lets in less.
Beyond exposure, aperture also plays a role in depth of field—the range of distances within a photograph that appear in focus. A wide aperture assists in creating a shallow depth of field (blurry background), while a narrow aperture helps keep more of the scene sharp. We’ll see this in action in the next lesson.
ISO
ISO represents the amount of amplification that occurs to the signal that the sensor receives. A higher ISO represents more amplification, and a lower ISO represents less amplification of this signal, with the greater the amplification resulting in a brighter image of the same scene. Higher ISOs also introduce grain or digital noise to the image - how much depends on individual cameras.
In film, ISO is a characteristic of the film itself and on digital cameras, you have the ability to adjust the ISO.
Disclaimer:
This is just a quick overview to set the stage for what we’ll cover in the coming weeks. What’s important to understand now is that these three settings don’t work in isolation—adjusting one affects the others. Controlling exposure is all about balancing them. Think of it as a carefully choreographed dance between aperture, shutter speed, and ISO to capture the perfect shot—and we’re about to learn the steps.