It refers to the lens opening of a camera.
The relationship between the f-stop or f-number and the size of the aperture is inverse. This means that the smaller the f-stop or f-number, the larger the aperture size.
The equivalent f-stop of the human eye is around f/2.1 to f/2.3.
focal
F-stop numbers are the numbers used to measure aperture (the amount of light entering the camera). Because f-stop numbers are actually fractions, the larger the f-stop number, the less light is entering the camera.
f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32 are the usual full stops in aperture. You could have a full stop difference between two half or thirds as well.a full stop is when the light is halved or doubled between the two settings. so in shutter speeds if the time is close to doubled or halved its considered a stop so going from 1/30th to 1/60th would be a stop and the next nominal stop down would be 1/125th of a second.
an f-stop is a setting for a camera lens that determines how much light is allowed to reach the film.
To change the f-stop on a Nikon camera, you can adjust the aperture setting using the camera's control dial or menu options. Look for the aperture setting labeled as "f-stop" or "aperture" on the camera display, and use the control dial to increase or decrease the f-stop value. A lower f-stop number (e.g., f/2.8) will result in a larger aperture opening, allowing more light to enter the camera, while a higher f-stop number (e.g., f/16) will result in a smaller aperture opening, letting in less light.
The cast of F Stop - 2008 includes: Torsten Schwick as Photographer
To change the f-stop on a Nikon camera, locate the command dial on the camera body. Turn the dial to adjust the aperture setting, which controls the f-stop. Lower f-stop numbers result in a larger aperture opening, allowing more light to enter the camera. Higher f-stop numbers result in a smaller aperture opening, letting in less light.
To calculate the f-stop of a camera lens, you divide the focal length of the lens by the diameter of the aperture opening. The f-stop is a measure of how much light the lens lets in, with lower f-stop numbers indicating a larger aperture opening and more light entering the camera.
When the f-stop of a camera increases in size the aperature also gets bigger
What lens? If your D3100 is using an f/5.6 (or f/5.8) aperture lens, that's as far as you can stop it down.