Exposure

Exposure is the total light a sensor receives for a given frame, controlled by three settings that trade against each other: aperture changes depth of field, shutter angle or speed changes motion blur, and ISO changes noise. Any exposure can be reached by several combinations of the three, and each combination looks different, so the choice is creative as much as technical. Two failure modes bracket it. Underexposing and lifting later brings up noise in the shadows, and overexposing clips highlights that no grade will bring back. Use the tools rather than the screen: a histogram, zebras or false colour tell you where you are, while a camera's display lies about brightness depending on how it is set.