To Photography Beginner : What is Aperture (f value) ?

What is aperture (f value)? If you want to become a  photographer, you must understand what is aperture before you think about other aspect.

The aperture is the parameter that decide how much light enter to your camera's sensor.
In other words, aperture decide the strength of the light that received by your camera's sensor.
When set to bigger aperture (lower f value), the sensor will receive more light and vice versa.
So, what is the usage of aperture ?

Control shutter speed (Fixed ISO value)
Shutter is the entrance of the light to the sensor. Provided fixed aperture and fixed ISO value, the higher the shutter speed, the lower the amount of light received by the sensor and vice versa.
If you set your shutter speed to very slow (for example 2 sec), the time for the light enter to your camera is relatively long, most likely your photo will be over exposed. Thus, you may need to set a faster shutter speed to get a correct exposure.
The bigger the aperture (lower f value), the faster the shutter speed needed to maintain the correct exposure.
When you increase the aperture for 1 stop, the shutter speed will double in order to get a correct exposure, for example

• f2  , 1/1000
• f2.8, 1/500
• f4  , 1/250
• f5.6, 1/125
• f8  , 1/60
• ...

Therefore, if you have a big aperture lens (low f value), your camera can achieve a higher shutter speed at night in order to get a correct exposure. This helps to avoid blur image due to handshake.


Control Depth of Field
The bigger the aperture (lower f value), the lower the depth of field, which mean the out of focus area will blur out easily. Big apperture is suitable for portrait, because you want to isolate  the object from the messy background.
When you use smaller aperture (higher f value), you will get a high depth of field image, high depth of field is suitable for landscape photography, because you don't want a blur mountain or blur sea in your picture.
Example image of different aperture and shutter setting:

Control sharpness of the picture

For modern lens that having 6 or 7 elements, the sharpest image is often obtained by using f/5.6-f/8.

We will describe detail further in later post. Stay tuned.