In underwater photography, what device opens to allow light to pass onto the sensor or film surface?

In underwater photography, the device that opens to allow light to pass onto the sensor or film surface is the shutter. The shutter is a mechanical or electronic component that controls the duration for which light enters the camera. When you press the shutter release, the shutter opens briefly to expose the sensor or film, capturing the image.

The aperture, while also crucial in photography, refers to the size of the opening through which light passes in the lens. It controls the amount of light and also affects depth of field but does not open and close in the same sense that a shutter does. The lens focuses the light onto the sensor, playing a vital role in image quality but not directly controlling the exposure duration. The viewfinder is where the photographer looks through to compose the shot, separate from the light control mechanisms. Understanding these components helps clarify their specific functions in the image capture process.