Aperture, Shutter speed and International Organisation for Standardization (ISO) form the basic building blocks in photography. You should be able to control these 3 features in accordance with the environment and situation. Aperture setting is one of the most important factors to get a perfect shot and so understanding aperture is very essential.

There will be situations wherein you will have to use higher and lower values for aperture opening. So, you should know the effect or the change caused through different aperture values.


What is Aperture?

Now, let’s see what Aperture is all about and what values to be set for a perfect shot? Aperture is an opening or the hole on the lens system through which light enters into the camera body. If larger the opening, more amount of light will enter the camera and vice versa. Aperture opening in a camera is denoted by the f-number. This number corresponds to the maximum possible opening of the aperture.

Every SLR camera lens will have an f-number, which is mentioned in its manufacturer’s specifications.  A normal Point and Shoot Digital camera will also have an f-number that is mentioned in the manufacturer’s specifications as well as in the user guide.


How is it calculated?

As discussed above, Aperture is denoted in f-number. Higher the f-number, smaller will be the opening and vice versa. If you are a beginner in the field of photography, thenthe question that comes to your mind immediatelywill be, which f-number should I select? The answer depends on many factors like, the subject which you are going to shoot, whether you want background blurs, or if you want a narrow DOF or wide Depth Of Field,e.t.c.

Let’s see, as to how the f-number of a lens corresponds to the aperture opening. This can be explained better by an example. Let’s consider the case of Canon EF 50mm f1.8 lens and Canon EF 50mm f1.4 lens. These are prime lenses (fixed focal length ones).

Canon EF 50mm f1.8 lens,

Maximum possible Aperture opening is: 50/1.8 = 27.78 mm (diameter of the opening)

Canon EF 50mm f1.4 lens,

Maximum possible Aperture opening is: 50/1.4 = 35.71 mm (diameter of the opening)

So,from the above example it is clear that lower the f-number, greater will be the aperture opening. Now, the question would be what is the use of a lower f-number? Lower the f-number, greater the amount of light entering the sensor, which is good for low light photography and stark night photography. Also you will get a good “Bokeh” (Background blur).


Aperture & Depth Of Field (DOF)

Aperture opening and DOF are inversely related. Higher the Aperture opening
smaller will be
the DOF. Since Aperture and f-number are inversely related, higher values of f-numbers corresponds to a greater depth of field.

For easier understanding, have a look at the table given below:






Higher f-number


f16 & Above

Larger DOF

More in focus

Lower f-number


f4.0 & Below

Smaller DOF

Less in focus


When to use Narrow Aperture?

If you want to bring all the objects in the scene that is been focused then you can go for a narrow aperture. Narrow aperture values are usually used by landscape photographers and by photographers who take group photos. Landscape photographers would want to bring all; foreground, background and middle section in the focus. So, they will go for a smaller aperture opening (higher value of f-number), usually in the range of f16 to f22.

Another point to be noted is that a higher f-number demands for a slower shutter speed. So you will have to keep your camera steady, either mounted on a tripod or need to keep it on a stable base.

When you shoot a group of people, you will have to use a higher f-number to bring all the people within focus.

Now let us see how change in f-number affects the background blur with
the help of some examples.

Below given shots are taken using Canon EOS 7D with Canon EF 50mm f/1.8 lens. The aperture value is varied from f/1.8 to f/22. Focus is locked on the teddy bear doll in the front and the aperture values were varied for each shot.


From the above pictures it is clear that for getting a good “Bokeh” you will have to use a lower f-number (larger aperture opening). For getting more things in focus you will have to use a larger f-number (smaller aperture opening).


When to use Wide Aperture?

Wide Aperture is required when you take portraits or taking pictures of birds and flowers. So, macro photographers, wildlife photographers and sports photographers will go for a wider aperture (lower f-number). The basic
intention of selecting a wider aperture value is to get a nice background blur.

For wildlife and sports photographers, they need to freeze the motion of the subject, which demands for a higher shutter speed value. In such situation they will have to go for the lowest possible f-number in the camera. Lenses having lower f-numbers are referred to as fast lenses. Now, the question is:What is this lower range of f-numbers? F-number below f/4.0 can be considered as a wide aperture. Most of these fast lenses are costly except for Canon’s EF 50mm f/1.8 lens.


Aperture, Shutter speed and ISO

Aperture, Shutter speed and ISO are the three pillars of photography.

Let’s see how the change in aperture values affects the other two parameters? If you have selected a lower f-number (wide aperture opening), say f2.0; you can go for higher shutter speeds with lower ISO values. So, you can shoot your subjects handheld. Since a lower ISO value can be selected, we can reduce the noise in the image. You will be able to get a nice background blur too.

Now, select a higher f-number (narrow aperture opening), say f16.0. This value brings more objects on the scene to focus. Higher value of f-number
demands for a slower shutter speed. So, you won’t be able to shoot the scene
handheld. If the lighting is too good, then
you can shoot it handheld provided you choose a higher ISO value (around 1600). But, there will be some amount of noise in the picture that has to be removed later while post processing. If you intend to go for a lower ISO value, you will have to use a tripod.


Also, go through this article, ABC Of Photography, to make your fundamentals more strong and to have a better understanding about the basics of three pillars in photography.