How to blur the background? This is perhaps one of the initial questions everyone asks after buying a new DSLR camera. There are many photography enthusiasts who buy a DSLR camera just because it allows to blur the background, though it is really important to learn how you can achieve that.
The background blue effect or the bokeh effect (technical term) makes the subject stand out by making everything in front and at the back of the subject out of focus. You can always get the desired blur effect using various editing software such as Adobe Photoshop, but capturing it in-camera is far better.
Depth of field controls the amount of blur in your background
The amount of blur in your background depends on how shallow the depth of field is. Shallow depth of field results in blur background effect whereas deep depth of field makes the subject as well as the background well focused. The depth of field in your photo depends on three factors.
What is Depth of Field?
The depth of field is the area that lies in front of and behind the subject, which appears to be in focus. In simple language, when you set the focus on a particular subject, there is some area in front and behind the subject that is acceptably sharp and in focus. This area which appears to be in focus is known as the depth of field.
A photo with shallow depth of field will have a narrow area in front and behind the subject which will be in focus, which means the background and the foreground will have more of blurry effect. Similarly, a photo with deep depth of field will have a wide area in front and behind the subject which will be in focus, which means that the background and the foreground will have less of blurry effect and will appear in focus.
Example of shallow depth of field:
Example of deep depth of field:
What are the factors affecting Depth of Field?
You must have heard a lot that the depth of field is controlled by changing the aperture f-stop value, which is true. But this is not the only factor which controls the depth of field, in total, there are three factors affecting depth of field:
a. Aperture f-stop value
b. The Focal length of the lens
c. Camera-to-subject distance
How does aperture affect the Depth of Field?
Aperture is one of the most-known factors which controls the depth of field. The easiest way to understand this is, the lesser the aperture value, the shallower will be the depth of field which is ideal if you need to create blur effect in portraits and macro photography.
- The smaller the f-stop number = the bigger will be the aperture opening = the shallower the depth of field (more blur effect)
- The higher the f-stop number = the smaller will be the aperture opening = the deeper the depth of field (less blur effect)
NOTE: Changing the aperture value will also affect the shutter speed. Reducing the aperture value will increase the shutter speed and increasing the aperture value will decrease the shutter speed.
How does focal length affect the Depth of Field?
As we all know, using a longer focal length lets us go closer to the subject, and using a shorter focal length lets us capture wider frame. This is not the only use of using different focal lengths.
By using a longer focal length, you can reduce the depth of field and achieve bokeh in the background as well as the foreground.
Example: This approach can be used in a situation when you want deep depth of field, but you do not want to increase the aperture value as the shutter speed will decrease. What you can do is use a wider focal length in order to increase the area which is in focus in front and behind the subject.
How does camera-to-subject distance affect the Depth of Field?
Camera-to-subject distance is basically the distance between your camera and the subject on which you would be locking the focus on. The closer your take your camera to the subject, the area in focus in front and behind the subject will keep on reducing, thus resulting in shallower depth of field. When you take your camera farther from the subject, the area in focus in front and behind the subject will keep on increasing, resulting is deeper depth of field.
This approach can be ideal when you are using the kit lens (18-55mm f/3.5-5.6) on 55mm to click a flower and the minimum aperture value you can use is f/5.6. As you can not use a smaller aperture value, in order to get shallower depth of field you can move closer to the flower. This will help you isolate the flower from the background and achieve more bokeh.
Example: As you can see in the images below, the photo which has been clicked from as closer distance has shallower depth of field as compared to the photo clicked from distance.
In order to get maximum background blur, you need to make sure that you use the smallest possible aperture value on your lens. Furthermore, You would need a lens with longer focal length, anything more than 85 mm would be ideal. You also need to make sure that you move closer to the subject in order to reduce the distance between the camera and the subject. All these three practices would result in maximum possible blur effect, thus separating your subject from the background.