Bokeh describes the quality of out-of-focus areas of an image. The word “bokeh” (pronounced as boh-keh) comes from the Japanese word “boke,” which roughly translates into English as “fuzziness” or “confusion.”
Bokeh: not synonymous with blurry background
It’s ironic then that the term bokeh engenders confusion as to what it actually means. While bokeh is attributed to photos that display a shallow depth of field, bokeh should not be used as a synonym for “blurry background.”
Bokeh is about the quality, not amount, of blur
Bokeh actually has little to do with the amount of blur. Rather, it has everything to do with the quality of the blur.
Different lenses render out-of-focus areas of an image in different ways, giving rise to subjective opinions as to what constitutes an artistically pleasing bokeh. The general consensus is that ideally, out-of-focus areas should have smooth transitions between tonal areas and that out-of-focus points of light should be smooth and round, not hexagonal.
At the very least, the blurred background should not distract the viewer’s attention from the main subject of the photo. This is especially important when shooting portraits.
How bokeh is effected
Further discussion of bokeh delves into whether out-of-focus points of light should be uniform all the way across or appear lighter or darker at their edges. The construction of a lens, the number of shutter leaves and the amount of light in a photographic situation all have an effect on the bokeh produced by that lens.
Connoisseurs of bokeh shop for camera lenses based on their preferred bokeh characteristics.
Some photographers have fun with bokeh, and incorporate out-of-focus points of light into their compositions.
Curious about the bokeh produced by your camera’s lens? To decrease the depth of field in your photographs, the best results are obtained by shooting at maximum aperture (smaller F number), a long focal length and a short distance to the subject.