Bokeh
In photography, bokeh (/ˈboʊkə/ BOH-kə or /ˈboʊkeɪ/ BOH-kay;[1] Japanese: [boke]) is the aesthetic quality of the blur produced in out-of-focus parts of an image, whether foreground or background or both.
Some photographers incorrectly restrict use of the term bokeh to the appearance of bright spots in the out-of-focus area caused by circles of confusion.
[6] Photographers may deliberately use a shallow focus technique to create images with prominent out-of-focus regions, accentuating their lens's bokeh.
This is derived as a noun form of the verb bokeru, which is written in several ways,[7] with additional meanings and nuances: 暈ける refers to being blurry, hazy or out-of-focus, whereas the 惚ける and 呆ける spellings refer to being mentally hazy, befuddled, childish, senile, or playing stupid.
The English spelling bokeh was popularized in 1997 in Photo Techniques magazine, when Mike Johnston, the editor at the time, commissioned three papers on the topic for the May/June 1997 issue; he altered the spelling to suggest the correct pronunciation to English speakers, saying "it is properly pronounced with bo as in bone and ke as in Kenneth, with equal stress on either syllable".
When used in portrait photography (for their "natural" perspective), the photographer usually wants a shallow depth of field, so that the subject stands out sharply against a blurred background.
[15] This may actually be desirable, as blur circles that are dimmer near the edges produce less-defined shapes which blend smoothly with the surrounding image.
In contrast, a catadioptric telephoto lens renders bokehs resembling doughnuts, because its secondary mirror blocks the central part of the aperture opening.
In the past, wide aperture lenses (f/2, f/2.8) were very expensive, due to the complex mathematical design and manufacturing know-how required, at a time when all computations and glass making were done by hand.
Some lens manufacturers including Nikon,[17] Minolta, and Sony make lenses designed with specific controls to change the rendering of the out-of-focus areas.
An apodization filter is used to soften the aperture edges which results in a smooth defocused area with gradually fading circles.
[21] The 'Sigma YS System Focusing' 135 mm f/2.8 also has an extra manually-moved component, intended to compensate for aberration at close-focus distances.
For low dynamic range images, an artificial neural network may be used to reconstruct the HDR light.
[30] An alternative mechanical mechanism has been proposed for generating bokeh in small aperture cameras such as compacts or cellphone cameras, called image destabilisation,[31][32] in which both the lens and sensor are moved in order to maintain focus at one focal plane, while defocusing nearby ones.
[33] In 2009,[34] a research group at MIT Media Lab showed that the bokeh effect can be used to make imperceptibly small barcodes, or bokodes.
