The shutter controls...

• A. The length of time the film will be exposed to light
• B. The amount of light that reaches the sensor
• C. The duration of the sensor's overall life
• D. The color temperature of the scene

Answer: (A)

Shutter speed is about how long the film or sensor is exposed to light. When you press the shutter, it opens for a set amount of time, and light accumulates on the film or sensor during that interval. If that interval is long, more light hits the surface and the image is brighter; if it’s short, less light hits and the image is darker. The shutter doesn’t determine how bright the light is in the scene—that’s controlled by the aperture and ISO—nor does it set color temperature (white balance) or the sensor’s lifespan. So the correct idea is that the shutter controls the length of time the film or sensor is exposed to light.