Number that equals the focal length of the lens divided by the diameter of the aperture.

It is the number that equals the lens' focal length divided by the diameter of the aperture. The smaller the F stop value, the more light you are allowing into the camera at any one time.

The measurement of light able to pass through the photographic lens.

This is the ratio of the focal length to the effective diameter of the lens (f/A). It is not a measure of the efficiency or the transmission value of the lens. The smaller the f number the more light is passed.

In a lens, the ratio of the focal length to its diameter. The smaller the F stop, the more light is passed. The F stop also effects the depth of field.

Light Factor (f)”. The ability of a camera lens to pass light. A value used to indicate the speed of a lens where the smaller the number the better the lens “a fast lens”, the normal f stop in CCTV lenses is f/1.4 or f/1.2. Each increase in f-stop decreases the amount of light passed through the lens by 50%. The normal f-stops are: f/1.0 – f/1.4 – f.