Bokeh and depth of field, both the techniques help the photographers in creating beautiful photographs. In the approach of photographing at lower f-numbers, the distinction between depth of field and bokeh vanishes and the hobbyists and enthusiasts often end up using the terms bokeh and DOF interchangeably. To photograph the aesthetics of the subject and the background, one should be clear about what DOF and bokeh stand for. To effectively use the two techniques, let’s have a quick view at depth of field, bokeh and the differences between the two.
What Is Depth Of Field
The depth of field refers to the area of sharp focus in a photograph. When taking a photograph, sometimes it may be desirable to have the entire image sharp and at other times you may be interested in focusing only a small portion of the scene. You can easily achieve the desired effect by tuning the camera to aperture priority mode for either high depth of field or shallow DOF.
A high depth of field is the scenario where everything in the plane of focus is in sharp focus. The shallow depth of field on the other hand is the technique of focusing only a small portion of the plane of focus resulting in effectively focused subject amidst defocused background and foreground elements. The shallow depth of field helps in profoundly separating the subject by beautifully blurring the background clutter.
What Is Bokeh
Bokeh is the aesthetic quality of blur in out of focus areas of the image. Bokeh is the terminology used for defining the quality of blur achieved at shallow depth of field. It refers to the quality of blurred imagery complemented by circular discs of light rendered by out-of-focus points of light.
The bokeh thus refers to the circular discs formed as the result of blurring the background. The pronounced bokeh effect is created when the camera is tuned for shallow depth of field. The effective brightness in the background of the subject renders beautiful imagery to the out-of-focus areas, thus, resulting in smooth, soft circular discs in the background.
The Difference Between Bokeh And Depth Of Field
The above definitions clarify the fact that the depth of field and the bokeh are not same. While depth of field is the technique of presenting the area of sharp focus, bokeh is the craft of artistically presenting the out-of-focus area of an image.
Bokeh is more of a qualitative aspect of the photograph. You can eventually identify the bokeh as good or bad, but there is no way to adjudge the depth of field in terms of qualitative adjectives. The DOF is determined by the camera-to-subject distance, the lens focal length, the lens f-number, and the format size or circle of confusion criterion. The bokeh on the other hand is influenced by the phenomena outside the focal plane like foreground / background brightness, lens aberration, speed of the lens, color and shapes & patterns of the subject, etc.
Thus we can say that bokeh is dependent on depth of field but depth of field is in no way dependent on the bokeh. The bokeh and the depth of field are two different techniques used for specific purposes. The sole purpose of depth of field is to represent the area of sharp focus in the photograph, whereas bokeh is artistic quality of out-of-focus area. The two techniques (shallow depth of field and beautiful bokeh effect) when used together produce stunningly beautiful and creative results.
Watch out the following articles (and discussion forums), for comprehensive difference between depth of field and bokeh.
You can also check out Wikipedia articles on depth of field and bokeh.
Also, have a look at the beautiful images shot at lower f-numbers for shallow dof and bokeh effect respectively.