Photography 101: Understanding ISO, Shutter Speed, and Aperture
The exposure triangle is a fundamental concept that both beginner and seasoned photographers must understand. There’s no magic button that a professional photographer can press to instantly capture great photos. They, too, must rely on the same basics that beginners must master.
Just like professional athletes who perfect the basics before advancing in their sport, photographers must also continuously revisit and refine their understanding of the fundamentals. When an athlete faces a slump, they return to the basics to regain their form. Photography works the same way—at every level, practicing the fundamentals is key to improving and maintaining skill.
So, let’s break down the basics of the exposure triangle.
The Three Legs of the Exposure Triangle
ISO – A term that dates back to the film era, ISO refers to the sensitivity of the film to light. In the digital world, it refers to the sensor's sensitivity to light. The sensor is located inside the camera body and plays a crucial role in determining how much light is captured.
Shutter Speed – This is the amount of time the shutter (the "doorway" to the sensor) stays open to allow light to reach the sensor. The shutter is also located inside the camera body, and its speed determines how long the exposure lasts.
Aperture – The aperture is the size of the opening in the lens that allows light to pass through to the sensor. This is controlled by the lens itself and plays a key role in both the exposure and depth of field of the image.
These are the basics of what each part of the exposure triangle does. Achieving a properly exposed photo can be done in many ways. The easiest method, and the first most photographers encounter, is using the automatic modes on your camera. Going fully manual isn’t necessary to take great photos—despite what some may say. Ultimately, when a photo is printed, the average viewer probably won’t be asking what mode the photographer used.
Each leg of the exposure triangle can be adjusted to either allow more or less light to reach the sensor. However, each adjustment has different side effects. The skill in photography comes from understanding the basics and how each setting affects the image, allowing you to use them to your artistic advantage. Let’s take a closer look at these effects.
The Effects of Each Leg of the Exposure Triangle
ISO – Most photographers recommend using a lower ISO (around 100) to get the best color and clarity in your photos. However, a lower ISO also means less light is captured by the sensor. As you increase the ISO, the sensor becomes more sensitive to light and can capture more with less available light. The downside is that as the ISO increases, you’ll start to see "noise"—grainy artifacts that are particularly noticeable in darker areas of the photo or when you zoom in. Thankfully, technology has improved, and modern cameras are better at handling noise. There are also post-processing tools available to help reduce or remove it.
Shutter Speed – The shutter speed determines how long the shutter stays open, allowing light to reach the sensor. A slower shutter speed will let in more light, which can be useful in low-light conditions. However, the slower the shutter speed, the more likely you are to capture motion blur, which might be undesirable if you’re photographing fast-moving subjects. In these cases, a faster shutter speed is needed to "freeze" the action. On the flip side, you may want to intentionally show motion, such as when photographing a fast-moving subject like a car or running water. In this case, a slower shutter speed can be used creatively to convey that sense of motion.
Aperture – Aperture controls the size of the opening in the lens, which directly affects how much light reaches the sensor. A larger aperture (represented by a smaller f-number) allows more light in, while a smaller aperture (larger f-number) allows less light in. The real trick with aperture, however, is understanding how it affects depth of field. A larger aperture creates a shallow depth of field, which can blur the background and isolate the subject. Conversely, a smaller aperture creates a deeper depth of field, where more of the image—from the foreground to the background—will appear in focus. This is particularly useful in landscape photography or when you want to ensure that everything in the frame is sharp.
Summary
Wow, this turned out to be longer than I anticipated! Let’s recap: We have three key adjustments to control how much light reaches the sensor—ISO, Shutter Speed, and Aperture. Understanding the basics of each is crucial for determining how to achieve a correct exposure. But it doesn’t stop there. Knowing the effects (both good and bad) of each setting, and using them to fuel your creativity, is what sets you apart from other photographers.
