Which exposure setting is primarily affected by changing the ISO?

The exposure setting that is primarily affected by changing the ISO is brightness. ISO measures the sensitivity of your camera's sensor to light. When you increase the ISO setting, you make the sensor more sensitive, which allows it to capture more light in a given amount of time. As a result, higher ISO settings lead to increased brightness in your images, especially in low-light conditions.

Conversely, lowering the ISO decreases the sensor's sensitivity, resulting in darker images unless other settings (like shutter speed or aperture) are adjusted to compensate. Therefore, adjusting the ISO can significantly impact the overall exposure of an image, ultimately influencing its brightness.

Shutter speed refers to the duration that the camera's shutter is open, while aperture controls the size of the lens opening. Both shutter speed and aperture can affect exposure but are not directly altered by changing the ISO. Contrast, on the other hand, refers to the difference between the darkest and lightest parts of an image and is influenced more by lighting and processing rather than ISO settings.