Description and examples of F-stop in photography

An F-stop are the 'f' numbers you find on the description of your camera (eg. f3.5). It also means the aperture of the lens and this 'f' number/figure tells you how much light will pass through the lens of the camera like the light passes through the iris of our eye.

Larger aperture size = allows more light through the lens of the camera (represented by a smaller f number, eg. f2.8)
Smaller aperture size = less light passes through the lens of the camera (represented by a larger f number, eg. f22).

These f-stop numbers range from f1.4 - f64 and can have a major effect on the exposure of an image and also the depth of field.

small f-stop = small depth of field (focuses on things closest to the lens which is good for close-up shots)
large f-stop = large depth of field (focuses on things near and far away from the lens like landscape photography)

Depth of field

The above images show how a small depth of field by using small f numbers. The coin image is using an aperture of f5.6 and you can see how the photograph has focused on the coin at the front and the background is more blurry. The same has happened in the image of the dog which has been taken using an aperture of f6.7.

These two images show a larger depth of field using higher f numbers to create this effect. In the image of the coins the photographer has used an aperture of f32 which has made the depth of field increase considerably compared to the other image of the coins. In the image of the landscape they have used an aperture of f11. This ensures that everything is clear and is in focus.

Exposure is affected by the combination and correct balance of shutter speed and aperture as per the below:

Small f-stop (f4.5) + fast shutter speed (1/1000 sec) = correct exposure

This is because the fast shutter speed lets in less light and the small f-stop lets in more.

Or:

Large f-stop (f22) + slow shutter speed (1/30 sec) = correct exposure

This is because the slow shutter speed means that there is more light coming in but the larger f-stop lets less in.