'Bokeh' is a Japanese word that simply means blur or haze. It refers to out of focus area in a photograph. To keep the subject in focus and the background out of focus is a popular technique among photographers and it is used to isolate the subject and make the photograph more appealing. 

In this article we will try to understand what depth of field means, what factors affect it and how to use it to create beautiful images.

Depth of field refers to the range of distance from the camera which is sharp in focus in an image. 

If depth of field is 1 meter starting 2 feet from the camera then anything which is nearer than 2 feet and farther than 1 meter 2 feet will be out of focus or blurred. Only subjects within the 1 meter range starting 2 feet from the camera will be sharp in the image. So in nutshell you may remember that Depth of Field (DoF) refers to region in focus and 'Bokeh' refers to region out of focus.

DoF depends on three factors:

  1. Aperture

    As aperture gets wider, depth of field gets smaller. At F/1.4 aperture depth of field is razor thin, specially close to the camera. Higher F numbers (F/8 or F/22) tend to produce a very wide depth of field which is desired for landscape photography. It means everything, starting few feet from the camera and all the way to very far away, will be sharp in the image
  2. Focal Length

    Tele-lenses  with  long Focal lengths, such as 200mm, Focal Plane is narrow even at high F - numbers such as f/8.0. So if you want smooth blurred background then grab the highest focal length lens available with you and shoot. On the other hand a Wide Angle lens, such as 14mm  will have a wide focal plane even at smaller F - numbers such as f/2.8. 
  3. Distance

    Distance of the subject from the camera and also the distance of the background from the subject also affects the depth of field in your photographs. Closer the subject is from the camera shallower will be the depth of field. 



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