What is Depth of field (DOF) ?
Depth of Field is the distance between the nearest and the farthest objects that are in acceptably sharp focus in an image.
When we take a picture , at a particular aperture and focal length there is a region before and after the Focal plane in which the objects will be acceptably sharp. It can be represented as below:
There are three main factors that can control the depth of field of your photo, they are:
- Aperture (f-value)
- The focal length of the lens.
- Distance from the camera to the subject.
1.Aperture (f-value) :
Let’s consider shooting at a fixed focal length. Now with the increase of f-value the DOF region also increases.
The DOF region for a f-value of say f2 will be shallower than the DOF region for f4 or f8 , below you can see how the DOF varies while f-value changes.
2. The focal length of the lens
Let’s consider we are shooting at a fixed aperture in different focal lengths , then the DOF will increase when the focal length decreases. Below image will show the relation between focal length and DOF.
3.Distance from the camera to the subject
When the subject is closer to the camera we will have a shallow depth of field or DOF, while the subject moves farther away from the camera , the DOF also increases. Technically we can say that when the focal point is closer to the camera the DOF is shallower and when the focal point is farther away from the camera , DOF is deeper.
Measuring DOF value ?
In early stages of photography there used to be DOF charts available for camera and lens combinations. Nowadays there are web and mobile apps available for finding the DOF. Below are few of them which you can use to find the DOF of your camera and lens combination.