Coarse bokeh on a photo shot with an 85mm lens and 70mm
aperture, which corresponds to f/1.2
In
photography,
bokeh (pronounced
/boʊˈkeɪ/) is the blur,
[1][2] or the aesthetic quality of the blur,
[3][4][5] in out-of-focus areas of an image, or "the way the lens renders out-of-focus points of light."
[6] Differences in
lens aberrations and
aperture shape cause some
lens designs to blur the image in a way that is pleasing to the eye, while others produce blurring that is unpleasant or distracting—"good" and "bad" bokeh, respectively.
[1] Bokeh occurs for parts of the scene that lie outside the
depth of field. Photographers sometimes deliberately use a
shallow focus technique to create images with prominent out-of-focus regions.
Bokeh is often most visible around small background highlights, such as specular reflections and light sources, which is why it is often associated with such areas.
[1] However, bokeh is not limited to highlights, as blur occurs in all out-of-focus regions of the image.
An example of the bokeh effect produced by a Canon 85mm prime f/1.8 lens.
200mm lens with a 100mm
aperture, which corresponds to f/2
The term comes from the
Japanese word
boke (暈け or ボケ), which means "blur" or "haze", or
boke-aji (ボケ味), the "blur quality". The Japanese term
bokeis also used in the sense of a mental haze or senility.
[7]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 March/April 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".
[2] Bokeh replaced the previous spelling
boke that had been in use at least since 1996, when Merklinger had also suggested "or Bokeh if you prefer."
[8]The term
bokeh has appeared in photography books at least since 1998.
[3] It is sometimes pronounced
/ˈboʊkə/ (boke-uh
[9]).
[edit]Description
The
depth of field is the region where the size of the circle of confusion is less than the resolution of the human eye.
Although difficult to quantify, some lenses enhance overall image quality by producing more subjectively pleasing out-of-focus areas. Good bokeh is especially important for large-
aperture lenses,
macro lenses, and long
telephoto lenses because they are typically used with a shallow
depth of field. Bokeh is also important for medium telephoto "portrait lenses" (typically 85–150 mm on 35 mm format) because in portraiture photography, the photographer typically seeks to obtain a shallow depth of field to achieve an out-of-focus background and make the subject stand out.
Bokeh characteristics may be quantified by examining the image's
circle of confusion. In out-of-focus areas, each point of light becomes an image of the aperture, generally a more or less round disc. Depending how a lens is corrected for
spherical aberration, the disc may be uniformly illuminated, brighter near the edge, or brighter near the center. Lenses that are poorly corrected for spherical aberration will show one kind of disc for out-of-focus points in front of the plane of focus, and a different kind for points behind. 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. Lens manufacturers including
Nikon and
Canon make lenses designed with specific controls to change the rendering of the out-of-focus areas.
The shape of the aperture has a great influence on the subjective quality of bokeh. For conventional lens designs (with bladed apertures), when a lens is stopped down smaller than its maximum
aperture size (minimum
f-number), out-of-focus points are blurred into the
polygonal shape formed by the aperture blades. This is most apparent when a lens produces hard-edged bokeh. For this reason, some lenses have many aperture blades and/or blades with curved edges to make the aperture more closely approximate a circle rather than polygonal. Traditional "Portrait" lenses, such as the "fast" 85mm focal length models for 35mm cameras often feature almost circular aperture diaphragms, as is the case with
Canon's EF 85mm f/1.2L II lens and
Nikon's 85mm f/1.4D, and are generally considered exceptional performers. In contrast, a
catadioptric telephoto lens displays bokehs resembling doughnuts, because its
secondary mirror blocks the central part of the aperture opening. Recently, photographers have exploited the shape of the bokeh by creating a simple mask out of card with shapes such as hearts or stars, that the photographer wishes the bokeh to be, and placing it over the lens.
[10]Leica lenses, especially vintage ones, are often claimed to excel in bokeh quality, although Leica photographers have tended to make more use of maximum aperture due to the lenses' ability to maintain good sharpness at wide openings and the suitability of the Leica camera system for available-light theatre work and reportage. Consequently, more evidence is needed to determine whether Leica's lens designers deliberately set out to produce pleasing bokeh.
Minolta/Sony STF 135mm f/2.8 [T4.5]* (STF standing for
Smooth Transition Focus) is a lens which is specifically designed to produce pleasing bokeh. An
apodization filter is used to soften the aperture edges which results in a smooth defocused area with gradually fading circles. Those qualities make it the only lens of this kind currently on the market.
Recently, a research group at
MIT Media Lab showed that the bokeh effect can be used to make imperceptibly small barcodes, or
bokodes. By using markers as small as 3mm with a small lens over them, if the marker is viewed out of focus through an ordinary camera focussed at infinity, the resulting image is large enough to scan the information in the barcode.
[11][edit]Emulation
Bokeh can be simulated by
convolving the image with a
kernel that corresponds to the image of an out-of-focus point source taken with a real camera. Unlike conventional convolution, this convolution has a kernel that depends on the distance of each image point and – at least in principle – has to include image points that are occluded by objects in the foreground.
[12] Also, bokeh is not just any blur. To a first approximation, defocus blur is convolution by a uniform
disk, a more computationally-intensive operation than the "standard"
Gaussian blur; the prior produces sharp circles around highlights whereas the latter is a much softer effect.
Diffraction may alter the effective shape of the blur. Some graphics editors have a filter to do this, usually called "Lens Blur."
[13]An alternative mechanical mechanism has been proposed for generating bokeh in small aperture cameras such as compacts or cellphone cameras, called image destabilisation,
[14][15] in which both the lens and sensor are moved in order to maintain focus at one focal plane, while defocusing nearby ones. This effect currently generates blur in only one axis.
Nikon D3100 Quick review : About a year ago Nikon presented the D3000, a 10.2 Megapixel DSLR camera with several features that we also saw in the Nikon D90 and the D5000. With the introduction of the Nikon D3100, the successor to the Nikon D3000, Nikon again has an amateur DSLR camera in its assortment with specifications and functions that are all up-to-date again. The resolution has increased quite a bit, from 10.2 to 14.2 Megapixels and the Nikon D3100 SLR camera now also offers Full HD video. Of course the Nikon D3100 camera offers Live View, and there are also new AF settings included. The Nikon D3100 is a digital SLR camera aimed at the amateur photographer. A DSLR camera that has user friendliness as a bonus.
