A Sense of Accomplishment Gone Wrong
More often than not, when the average amateur photographer learns briefly what bokeh means, it gives them a boost of confidence with their photography. They feel a sense of superiority, like they have a much more distinguished point of view as a photographer. As a matter of fact, sometimes it really does make their photographs look quite a bit better due to the fact that bokeh is now on their conscience and somewhat of a priority. However, when they hear or even see the word "bokeh" they almost always automatically think depth of field. While this may not be an altogether false assumption, depth of field does in fact cause bokeh, it is usually more of an assumption of ignorance rather than anything else.
The Real Difference
As mentioned before, the term "bokeh" is often confused with the term "depth of field" – I’ve been guilty of it, you’ve probably been guilty of it, and almost all photographers who take their work seriously are most likely guilty of it at one time or another. The important thing to realize is that depth of field is the amount of picture that is in focus, not the amount that is out-of-focus. While depth of field does cause bokeh, bokeh does not cause depth of field. Perceiving depth of field this way, it is possible to have a photograph with very large depth of field, where there is very minimal bokeh. Having this knowledge within itself can give you the ability to stand out as a photographer.
Bokeh as it Truly is
Bokeh does not only mean the out-of-focus part of a photo, it also means the quality of that out-of-focus area. Bokeh is the word that describes the appearance of an out-of-focus area and its disposition. Some lenses have better quality bokeh than others, and some lenses have the ability to present more shallow depth of field – resulting in more bokeh. Commonly, "good" bokeh is an out-of-focus area that is very silky smooth and has no rough or sharp edges. An important rule of thumb to remember is that sharp edges should be left solely for the focused area of a picture, whereas the out-of-focus part should look very soft and smooth with no real edges of any kind.
(Click on images to enlarge)
An Example of Good Bokeh
Understand it and Apply it
When shooting, photographers should always consider how depth of field and bokeh work together. It can be a vital step to really keep in mind where to use depth of field as well as the quality of bokeh that needs to be achieved. Should a subject in your photo be solely focused on with a shallow depth of field, or are you creating a landscape shot that needs a large depth of field to visually capture more detail? The choice is purely up to you, but it is your responsibility as a photographer to decide how and when to use it appropriately. This can, within itself, determine whether people perceive you as an amateur or professional photographer – It can even separate you from other professionals.