What is aperture in digital camera?

Aperture refers to the opening of a lens's diaphragm through which light passes. It is
calibrated in f/stops and is generally written as numbers such as 1.4, 2, 2.8, 4, 5.6, 8, 11 and
16. Lower f/stops give more exposure because they represent the larger apertures, while
the higher f/stops give less exposure because they represent smaller apertures. This may
seem a little contradictory at first but will become clearer as you take pictures at varying
f/stops. Be sure to check your manual first to learn how to set Aperture Priority for your
camera, then try experimenting to get comfortable with changing the aperture and
recognizing the effects different apertures will have on the end-result image.





How Aperture Affects Depth of Field

Depth of field is the zone of acceptable sharpness in front of and behind the subject on
which the lens is focused. Simply put: how sharp or blurry is the area behind your subject.
The lower the f/stop—the larger the opening in the lens—the less depth of field—the
blurrier the background.
The higher the f/stop—the smaller the opening in the lens—the greater the depth of
field—the sharper the background



How Aperture Affects Shutter Speed
Using a low f/stop means more light is entering the lens and therefore the shutter doesn't
need to stay open as long to make a correct exposure which translates into a faster shutter
speed. Again, the reverse is true: using a high f/stop means that less light is entering the
lens and therefore the shutter will need to stay open a little longer which translates into a
slower shutter speed.

  

How to Choose Aperture

Now that we know how to control depth of field, what determines the choices we make in
selecting the aperture? We use focus and depth of field to direct attention to what is
important in the photograph, and we use lack of focus to minimize distractions that cannot
be eliminated from the composition. While there are no rules, there are some guidelines for
selecting Aperture priority

Aperture for Intermediate Depth of Field

While we can get the maximum or minimum depth of field by working at each end of the
aperture range, sometimes we want a more intermediate level of depth of field, limiting
focus to a specific range of distances within the overall photograph. One way to do this is
to choose a mid-range f/stop, like f/5.6, and shoot a test frame. In image playback, use the
magnifying function of the LCD to zoom in and check the depth of field; make adjustments if
necessary and reshoot.