Quite frequently photographers use shallow depth of field so as to make the main subject stand out. However many photographers forget the effects of this blurred background on the overall image. Bokeh is a fancy term that is used to indicate this out of focus area.

(Decorative lights with Bokeh – captured with a 135mm lens at f/2.8, 1/160 sec)

Achieve shallow depth of field

This is the first prerequisite to get good bokeh. Shallow depth of field can be achieved by any of these and more frequently a combination of these factors –

A large open aperture (small f-number). f/2.8 will throw most of the things out of focus, in front and behind the subject. Whereas an aperture of f/11 will get most of the things to appear clear extending from front of the subject to far behind.

An interesting thing to note here is that the area of focus (hyperfocal distance) covers 1/3rd of the distance towards foreground and 2/3rd of the distance towards background from the plane of focus. So for example if you have focused at an object 4 meters from the camera at an aperture which is gettings things upto 2 more meters behind the focal plane also into focus, then upto about 1 meter of the foreground will also be in focus. The hyperfocal distance for this example will extend from 3 meters from the camera to 6 meters from the camera. (Staying Focused)

Long focal length. In wide-angles, getting shallow depth of field is difficult. Whereas in long tele lenses, the depth of field remains shallow even at moderate apertures. This is also one of the reasons why getting shallow

Relative distance between the main subject and out of focus areas is important. Greater the distance between the main subject and the background, easier it is to blur the background.

Distance from the camera also matters. The closer the subject is to the camera, the shallower the depth of field will be. Macro photographers use very small aperture sizes and yet end up getting blurred backgrounds. Place your subject close to the camera and it’ll be easier to throw the background out of focus.

(Plastic flowers in a super-market. Nikon Df with 135mm lens, f/2.8, 1/160 sec.
Notice the out-of-focus background which has retained enough details to show the super-market shelves and a person moving around.)

Getting quality bokeh
Good quality bokeh makes the photographs visually appealing. Bokeh adds to the overall composition and can make the photograph strong. So what exactly is good bokeh? Is it simply out of focus background? Some photographers limit the use of terms to parts of out of focus areas that have some kind of margins like any bright spots. I prefer to call the whole blurred background as Bokeh and the quality of Bokeh depends on many factors over and above simple blurring. Creating captivating photographs by good use of this technique can do wonders for photographs.

Color Theory
Good Bokeh should bring out the character of the main subject. Position the subject in such a manner that the subject stands out in front of the background. A red rose may look good against green blurred background of the leaves. A white bird may look good against the blurred greens of the vegetation but may not be so effective in front of white-grey skies. Have a background that does not call attention to itself.

Excessive blurring is not good
Do not equate good Bokeh with the widest open aperture and the highest possible blur. The background should have a character to it. Sometimes the blurred background itself maybe a secondary element, adding substance to the photograph. Maintain a good balance between the focused subjects and blurred backgrounds. Very often the background may relate to the subject. Some amount of blurring will bring the subject out but retaining some recognizable features of the background are also important.

Quality of Bokeh and Lens
Lens construction also contributes to good looking Bokeh. Out of focus lights may look like doughnuts with mirror lenses, hexagons with lenses having six leaves of straight aperture blades or round unfocused spots with lenses having large number of curved aperture blades. Lens microcontrast, an often debated topic also plays an important role in making the bokeh pleasing. Soft focus filters can enhance the overall presentation of the bokeh. Nikkor Defocus Control lenses are champions when it comes to manipulation of Bokeh while keeping the subject sharp. Lensbaby and Petzval lenses add their own character. A lot depends on the lens too. (Tilt Shift movements allow significantly better control on planes of focus and consequently bokeh. These deserve an entirely another article, which I hope to write sometime soon.)

Effects of aperture shape
As described above, the shape of aperture is reflected in the bokeh. Round aperture blades create round out of focus areas. Going a step further, cutting interesting shapes out of dark paper and taping them to the front of the lens creates bokeh in the shape of the cut-shape. This can be an interesting experiment but nothing more than that. I have mentioned it here just for the sake of completeness of this article.

Post-processing
Common photo-editing programs provide a bouquet of power blur-tools. These may mimic the effects of good bokeh but I suggest keeping their use to the minimum. These are very powerful tools and can quickly turn a simple photograph into a photo-editing disaster. So be very careful while using them, or better still, avoid them.

(Bamboo leaves – faint outline of the leaves behind adds to the fullness of the composition.
A shallower depth of field would have taken away this feeling.)

Focus on your bokeh (I like the pun here), and be ready to be pleasantly surprised. Just a bit of pre-planning can make masterpieces out of mundane photographs. Think beyond blurred background and tread into the creativity of good bokeh.

(Sometimes the bokeh itself can be the subject.)