If you’ve ever looked at a photo and thought, “Why doesn’t mine look like that?” Chances are, it’s exposure. Understanding how light hits your camera’s sensor is one of the most important skills you’ll ever develop as a photographer. It’s not guesswork; it’s science, and it all comes down to three settings: aperture, shutter speed, and ISO, a relationship known as the Exposure Triangle.

In this guide, you’ll learn how to control exposure with precision, avoid blown-out highlights or muddy shadows, and make every photo feel intentional. Whether you're new to photography or want to shoot with more confidence, this is where it all begins.

What is the Exposure?

Exposure refers to how much light your camera sensor captures when taking a photo. It directly affects how bright or dark your image appears.

Underexposed – Too little light hits the sensor, resulting in a dark image.
Overexposed – Too much light hits the sensor, washing out highlights and detail.
Correctly Exposed – The image has detail in both shadows and highlights, with nothing completely lost.

The Exposure Triangle is the relationship between your camera’s three core settings:

Aperture
Shutter Speed
ISO

Each setting affects the amount of light that reaches your sensor, and adjusting one will often require changes to the others.

Aperture

Aperture (measured in f-stops like f/2.8, f/5.6, f/11) controls how much light enters through your lens.

Lower f-number (e.g., f/1.8) = Larger opening = More light
Higher f-number (e.g., f/16) = Smaller opening = Less light

It also affects the depth of field, or how blurry the background is.

Shutter Speed

Shutter speed controls how long your camera sensor is exposed to light.

Fast shutter (e.g., 1/1000 sec) = Less light, sharp motion
Slow shutter (e.g., 1/30 sec) = More light, motion blur

Every time you halve or double the time, you're adjusting the exposure by one stop of light.

ISO

ISO refers to your camera sensor’s sensitivity to light.

Lower ISO (e.g., 100) = Less sensitivity = Cleaner image
Higher ISO (e.g., 1600+) = More sensitivity = Brighter image, more grain

Doubling your ISO increases exposure by one stop, but also increases noise.

Stops of Light

A stop is a measurement of light. Changing exposure by one stop means doubling or halving the amount of light.

Examples:

ISO 100 to ISO 200 = +1 stop
1/250s to 1/500s = -1 stop
f/2.8 to f/4 = -1 stop

Putting it All Together

Let’s say your camera settings are f/8, 1/60, ISO 200 and you wanted to open up your aperture to f/2.8 for a shallower depth of field. To keep the SAME level of overall brightness (exposure), you could change your shutter speed to 1 /500 (or -3EV) to compensate for that change. Alternatively, you could change your ISO to 100 and your shutter speed to 1/250 (f/2.8, 1/250, ISO 100) for the level of overall brightness.

For example, the following settings would produce the same level of overall brightness in the image:

f/8, 1/250, ISO 400

f/4, 1/500, ISO 200

f/16, 1/30, ISO 200

To Make Things Even Easier to Remember

A stop of light is double or half the amount of light in regards to the overall exposure of an image.
Doubling your shutter speed will DECREASE your overall exposure 1-Stop.
Doubling your aperture will DECREASE your overall exposure 1-Stop.
Doubling your ISO will INCREASE your overall exposure 1-Stop.

Mastering the Exposure Triangle: A Beginner’s Guide to Perfectly Lit Photos