A camera works by using a converging, light-focusing lens to let light enter the camera box. The light creates an image by causing a chemical reaction on photo film or an electrical reaction on digital medium.
A film camera uses a light-sensitive strip coated with silver halide to create and store the image, called a negative. The film must be developed using chemicals to produce photographs, usually on photo paper. The degree to which the speed and size of the shutter opening, as well as the position of the lens, can be manipulated depends on the complexity of the camera.
Digital cameras use a grid of photo sensors to record the incoming light, converting it into an electrical current. The amount of the current varies by the amount of incoming light, and the in-camera computer combines the different levels into a pattern that represents that light, in the form of an image. Digital cameras can display images on a screen instantly after being recorded, and provide the ability to edit, store or delete these images from the memory card. Most digital cameras have functions that allow for certain parts of the picture to remain in focus, and the ability to control the exposure setting so that the picture is neither too dim nor too bright. Data displays also allow the user to change settings like shutter speed and ISO speed instantly.