F Stop definition
A scale that measures the size of the opening of the iris on a camera’s lens. When one opens the iris wider, more light is allowed to expose the film. Closing the iris permits a less amount of light to enter the camera. The smaller the number of the f-stop, the wider is the opening of the iris (and vice versa). A standard f-stop scale is 1.4 - 2 - 2.8 - 4 - 5.6 - 8 - 11 - 16 – 22.