What are the two main exposure controls in a camera?

1. Shutter Speed

2. Aperture

3. ISO

When shooting film, changing ISO requires changing to a different roll of film. Since each roll has its own constant ISO value.

Since they can be changed between each shot, shutter speed and aperture are considered the two main exposure controls.

With digital sensors, ISO can be modified for every shot making it an additional "main" control in camera.