So what exactly is DOF? DOF can be rather confusing and put simply, DOF allows the photographer to control what will be in and out of focus in a picture.
It determines whether or not the subject, the foreground and the background can be sharply focused at the same time.
When the foreground, background and the subject of interest are all in focus, this is referred to as deep focus.
The opposite of deep focus is shallow focus where only the subject becomes the focal point of the photograph.
A shallow DOF draws attention to the subject of interest while creating a distance from everything else in the background and/or foreground.
DOF allows a photographer to be creative in determining what should be in and out of focus.
DOF depends on the aperture setting (F-stop number), focal length of the lens and the subject distance from the camera.
An aperture is the size of the opening which allows light to go through the lens.
It is expressed in F-stops or f/value.
I am using a Panasonic Lumix DMC-FZ35 which has an aperture range from f/2.
8 to f/8.
This means that the maximum aperture is at f/2.
8 and the minimum aperture is at f/8.
In general, a large aperture (small f/value) gives a shallow DOF and a small aperture (large f/value) gives a deep DOF.
Since the aperture opening determines the amount of light into the lens, the shutter settings should be adjusted accordingly to get the correct exposure with the different f/values.
Focal length of the lens is inversely proportional to the DOF which means that the shorter the focal length of the lens the deeper the DOF and vice versa.
As the focal length of the lens increases, its angle-of-view narrows.
Wide angle lens has a large angle-of-view and can take in lots of the scenes giving a greater DOF.
Hence both the subject and the background would be in sharp focus.
A lens with long focal length (telephoto lens) reduces the distance of the subject to the camera.
The angle-of-view of such lens is reduced to a few degrees and only takes in little of the scenes.
Therefore the effect is a shallow DOF.
Lastly is the distance of the subject from the camera.
The closer the subject of focus is to the camera, the shallower the DOF compared to a subject farther away from the camera.
After understanding the theory of DOF, the best way to learn and master it is to get out there and play around with the different settings to create photos with different DOF.
It is only practice which will make perfect.
Just enjoy the learning process and see how amazing and creative the photographs can turn out to be.