Aperture

The opening of the lenses are specified in terms of f-stop value which are expressed in numbers: f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22 etc. The examples shown are one (1) stop increment. Between them are 1/3 of a stop by default in digital cameras. Every time you turn the aperture dial towards to the left or right it increases/ decreases by 1/3 of a stop by default. (Note: There is also an option in your camera setting that you can increase/ decrease by 1/2 of a stop but most photographers use 1/3 of a stop.)

Do I have to memorize the examples? Yes! You'll see in the succeeding articles why it's important and how you are going to decide your exposure with your "reciprocals" using the exposure values of your aperture, shutter speed and ISO. It's not hard to memorize the example, you can see that there is a pattern in every increment of a stop by multiplying it by 1.4 and rounding it to a whole number or alternately it doubles in figure. Below are examples of the opening of an aperture, from large (smaller figures) to small (large figures) values. If you're more into the technical side, check out the video from Imre Z. Balint.

Fig 1. Examples of aperture opening

Aperture Revisited by Imre Z. Balint