APERTURE

Aperture is the lens diaphragm opening inside a lens. The side of the opening in this diaphragm regulated the amount of light which reaches the film, when the camera's shutter is opened.  The size of this aperture opening is referred by the term F-STOP. The F-STOP is calibrated so certain size of the opening in the aperture. These numbers are usually engraved in one of the lens's rings. As an example you these F-Stop numbers would be  F/22, F/16 ,F/8, F/5.6, f/4  and so forth. Depending on your lens you might fine more aperture setting numbers 

of less. Nevertheless you will always find some combination of these numbers made available for any given lens. 

WHAT IS A F-STOP

As mentioned above each of these values represent the amount o light which reaches the film during when the shutter is opened.

As you can note from the above diagram you can see how the F-Stop numbers effect the opening of the aperture. In more detailed terms selecting a lower f-stop will let in one times more light than the next higher f-stop.

for example f-11 will let 1 times more light than f-16, same applies to using the F-stop in the reverse order, where the amount of light will be reduced by a factor of 1, than the higher F-stop. An Easy way to remember and to master the technique of selecting the aperture is to remember the following.

A HIGHER F-STOP will result in a Small opening hence less light.

A LOWER  F-STOP will result in a Bigger opening, hence more light.

A More easier way is to REMEMBER :       

                                    BIG           f-STOP NUMBER   SMALL   APERTURE

                                    SMALL       f-STOP NUMBER     BIG     APERTURE

Once you have got your head around this, you can start to enjoy the use of you camera and understand the simplicity of photography.

HOW TO USE F-STOP

Using different aperture setting will effect the end result. There is a whole area called the depth of field to be explored under this section. But for now lets keep this simple. 

Apart from giving you control on the amount of light which reaches the film during exposure, the f-stop setting will also effect how much of the subject matter is in focus in the photograph.

As a simple rule of thumb, using a small F-Stop (which means your aperture is large ) will result in most of the background and foreground being thrown out of focus, thus resulting in a photograph where the subject is is main focus. Alternatively using a large F-Stop (small aperture) will give you am image where everything in the frame is in focus.

Image 1                                                                                                  Image 2

Observe the above two images. In the first image more or less everything in the frame is within an acceptable focus. To achieve this I used a large F-Stop (F-16, small aperture), For the second image I did not want anything in the background to distract the image, hence I used a small F-Stop (F-4, large aperture), which resulted in only the flower being in focus, but everything around if being thrown out of focus.

WHAT ELSE

Apart from controlling the amount of light which reaches the film, the aperture also controls a feature called "Depth-Of-Field". For beginners I suggest that you  understand the fundamentals first before going onto Depth of field.