What does ISO measure in photography?

ISO measures the light sensitivity of the image sensor or film in photography. This sensitivity determines how well the camera can capture light; a higher ISO setting means greater sensitivity, allowing for photography in lower light conditions. Conversely, a lower ISO setting is used in bright settings, yielding images with less noise and higher quality. This aspect of ISO is crucial for photographers to understand, as it directly impacts the exposure and overall quality of an image, especially when balancing it with shutter speed and aperture.

The other options relate to different components of photography. The shutter speed affects how long the camera's shutter remains open, influencing motion blur and exposure time. The lens aperture size controls the amount of light entering the camera and affects depth of field. The color balance pertains to how colors are rendered in the image, often adjusted in post-processing or through specific camera settings, but does not relate to the sensitivity of the sensor or film. Understanding ISO allows photographers to make informed decisions about exposure and the overall aesthetic of their images.