Bokeh is a very popular photographic effect referring to the aesthetic quality of an out of focus area in the image. Bokeh can have different appearances. Smooth round dots as Robert used in his sample. Multi-sided geometric shapes like hexagons, caused by the number of blades in the lens, and everything in between.
There are numerous variables responsible for such different appearances of the bokeh, such are:
I am sure photography rocket scientists can make all kinds of formulas explaining the correlation of all those factors, but we can spare our brain cells and instead use the good old trial and error technique.
Photo by Robert Grant
1. Set up (or find) a background that will have a potential to produce good bokeh. If working in studio / home environment poke holes in dark background paper and project light from the back. (as demonstrated in the video above) Alternatively use Christmas lights or background with strong contrast in details.
2. Focus your lens close. Manually turn the focusing ring to the minimal focusing distance, the opposite side of infinity. You may use an object or a person as your subject. Make sure the background is far enough from the subject to allow your lens to produce a shallow DOF, depth of field. (blur / bokeh)
3. Test you lens at various f-stops. Adjust shutter speed to compensate for the correct exposure. Or use “A” / “AV” setting for aperture priority, the camera will adjust the shutter speed automatically while you are changing f-stops. Please note that the difference in appearance of bokeh will vary greatly even with a sublte change of ½ f-stop. Often ½ f-stop change will turn a circle into heptagon, or other shape depending on how many aperture blades your lens has and handful other variables mentioned above.
4. Test, test and test some more. Change distance between camera and subject, subject and background, focal point, f-stops, test all your other lenses, test with different focal length.
Once you get the look you really like shoot some good creative images and post your shots here, using the “share your shot feature” in comments. Patience, Persistence, Bang !