Which statement about ISO is true?

• A. It measures color temperature
• B. It refers to the sensitivity of the sensor to available light
• C. It controls the duration the shutter is open
• D. It sets the aperture size

Answer: (B)

ISO represents how sensitive the camera sensor is to light. A higher ISO means the sensor is amplified to be more responsive in low light, which lets you shoot without slowing the shutter or opening the lens as much, but it also introduces more noise or grain in the image. This makes the statement that ISO refers to the sensor’s sensitivity to available light the correct description. Color temperature is about white balance and is measured in Kelvin, not ISO. The duration the shutter is open is shutter speed, and the aperture size is the lens opening controlled by the f-number; neither of these are what ISO describes.