Light is so important to video. One can spend their lives doing nothing but figuring out what light to put where in order to create a mood in an image.
Light comes from a source — like a sun or a lamp — bounces off objects, passes through your camera’s lens and lands on the sensor where its intensity is registered. Bright light registers differently from darker light and all your sensor does is map where that light falls and how strong it is. If all the light has similar strength, your image is evenly lit, if there are strong fluctuations, your image will have high contrast.
