History: Color Photography By Sergey Prokudin-Gorsky, Russia, 1915

Inherent sensitivity of the medium to light intensity and color/wavelengths.
The nature of the light recording material, for example its resolution as measured in pixels or grains of silver halide.
Camera controls are inter-related. The total amount of light reaching the film plane (the "exposure") changes with the duration of exposure, aperture of the lens, and on the effective focal length of the lens (which in variable focal length lenses, can force a change in aperture as the lens is zoomed). Changing any of these controls can alter the exposure. Many cameras may be set to adjust most or all of these controls automatically. This automatic functionality is useful for occasional photographers in many situations.