Comprehending Exposure (Aperture, Shutter Speed, ISO)

Understanding Exposure

Exposure refers to the amount of light that hits the camera’s sensor to create an image.
It’s controlled by three main camera settings: aperture, shutter speed, and ISO. Together, these three elements are known as the exposure triangle.
Adjusting any of these settings can change how bright or dark the image appears (its exposure), as well as affecting other aspects of the photo.

The aperture of a camera is the opening in the lens that lets light in.
Aperture sizes are measured in f-stops e.g., f/1.4, f/2, f/2.8, and each f-stop represents a “step” in light.
A smaller f-stop number, like f/1.4, indicates a wider aperture (more light entering the camera), while a larger f-stop number, such as f/16, means a smaller aperture (less light entering the camera).
Aperture also impacts the depth of field. A wide aperture (small number) will give a shallow depth of field (objects in the foreground in focus, background blurry), while a small aperture (large number) provides a deep depth of field (more of the scene is in focus).

The shutter speed determines the length of time the camera’s shutter is open and exposing the sensor to light.
It’s measured in seconds or fractions of a second.
A fast shutter speed (like 1/1000th of a second) lets in less light and freezes motion, while a slow shutter speed (such as 1 second) lets in more light and captures motion as blur.
Therefore, shutter speed is key for showing movement in your photos. Fast shutter speeds can freeze action, while slower speeds can create a sense of motion.

ISO is the camera’s sensitivity to light.
A low ISO number (e.g., 100 or 200) means less sensitivity to light but gives clearer, less noisy images.
A high ISO number (e.g., 800, 1600 or higher) increases the camera’s light sensitivity but produces more noise (graininess) in the image.
Typically, you’d choose a low ISO for bright conditions to ensure the image isn’t overexposed, and a high ISO for darker conditions or when you need a faster shutter speed.

When photographing, one needs to balance aperture, shutter speed, and ISO to achieve the desired exposure.
Altering one aspect of the exposure triangle often requires adjusting the others to compensate. For instance, if you choose a wide aperture to blur your background (small f-stop number), you might need a faster shutter speed to avoid overexposing your image.
Mastering the interaction between these three elements, and understanding how to manipulate them to achieve your desired results, is a key element of photography.