DIAPRAGHM
The diaphragm is a hole in place of light entering the camera lens when taking the picture. The diaphragm has several sizes or numbers. Each lens has different diaphragm openings respectively. Usually, the size of the diaphragm starts with 2,8-4-5,6-8-11-16-22. The size of aperture diaphragm that we choose to produce different images.
small aperture will produce a vast space. and large diaphragm will create a sharp narrow space (Blur). Or simply, it means opening the lens diaphragm.
In effect, the greater the aperture, the greater the speed required, the higher speed. Other effects, the bigger the aperture, the sharpness of a narrow space, which means that the greater the blur effect for the area outside the room sharp focus.
Many ways and purpose of the use or selection of the diaphragm, which among others will certainly affect the context of the photos that we make. For example: to photograph landscape, using any camera, try setting to the most narrow aperture (largest number) that may be achieved, then balanced with a long exposure time settings as necessary (note the light meter).
But especially for shooting night, sometimes we can not reach the most narrow openings because of limited exposure time shutter that can not be too long, especially in the prosumer cameras are usually limited to 13 seconds maximum.
Fortunately for prosumer digital cameras this is not a problem, because the sensor size is far smaller than a 35mm film frame, the space still sharp wide enough, even though the diaphragm is set to f/3.5 for example.
And, it all depends on how the photo we will create.
