What is the F in F-stop?

Answer 1

It is a measure of the size of the opening in the lens for the light to pass through.

The smaller the f-stop the larger the lens opening, and large f numbers relate to small openings or apertures in the lens.

Answer 2

Full

Actually it means "function". The 'f' in 'f-stop' is a mathematical function representing the focal length of the lens divide by the diameter of the aperture. For most lenses, the f-number is expressed as a maximum and indicated as, for example, '1:2.8'.

If the lens is a 200mm focal length and the diameter of the iris when fully open is 71.5mm, the the maximum aperture is 2.8 and is expressed on the lens as 'f=1:2.8'

More often than not, you cannot measure the objective of a lens and arrive at the f-number because the aperture is located deeper within the lens body.

Answer 3

F stop (focal stop) is a value that indicates the size of the lens aperture used during the taking of a photograph. The aperture is the size of the opening in the lens that allows light to enter the camera and expose the film or act on the image sensor. A small aperture is represented by a large number; a large aperture by a small number. That is:

- f/2.8 (or F2.8) indicates a large aperture (opening) lets in more light

- f/16 (or F16) indicates a small aperture (opening) lets in less light

The typical values in between these are: F4 F5.6 F8 F11. While confusing to many, it can be easier to understand if you learn that the value relates to the number of times the aperture will fit into the lens' focal length. Obviously, for a 50mm lens, an aperture diameter that fits in only twice (25mm which gives F2) has to be larger than one that cant fit into 50mm 8 times (F8). As we go from smallest aperture to largest, each full increment doubles the amount of light that enters the camera.

The values used herein are for explanation purposes only. Many lenses are capable of f numbers that likely include those mentioned here, but may also have numbers below and above.

Answer 4

"f stop" is the "focal ratio" of how much light does your camera allows to enter to the camera's sensor chip. It is like a window, as you close it more to 100% (increase the F in your camera) as it will be harder for the air to get in (the light in this case)

Answer 5

focal length

Answer 6

focal