Bokeh

For other uses, seeBokeh (disambiguation).

Not to be confused withDepth of field.

Coarse bokeh on a photo shot with an 85 mm lens and 70 mmentrance pupildiameter, which corresponds tof/1.2

An example of a portrait photo (ofKatherine Maher). Note the 'swirly' bokeh.

How the bokeh varies with the aperture.

Inphotography,bokeh(/ˈboʊkə/BOH-kəor/ˈboʊkeɪ/BOH-kay;Japanese:[boke]) is the aesthetic quality of the blur produced inout-of-focusparts of an image, whether foreground or background or both. It is created by using a wide aperture lens.

Some photographers incorrectly restrict use of the term bokeh to the appearance of bright spots in the out-of-focus area caused bycircles of confusion.Bokeh has also been defined as "the way thelensrenders out-of-focus points of light ".Differences inlens aberrationsandapertureshape cause very different bokeh effects.Some lens designs blur the image in a way that is pleasing to the eye, while others produce distracting or unpleasant blurring ( "good" and "bad" bokeh, respectively).Photographers may deliberately use ashallow focustechnique to create images with prominent out-of-focus regions, accentuating their lens's bokeh.

Bokeh is often most visible around small backgroundhighlights,such asspecular reflectionsandlight sources,which is why it is often associated with such areas.However, bokeh is not limited to highlights; blur occurs in all regions of an image which are outside thedepth of field.

The opposite of bokeh—an image in which multiple distances are visible and all are in focus—isdeep focus.

Etymology

The term comes from theJapanesewordboke(Vựng け/ボケ),which means"blur"or "haze", resulting inboke-aji(ボケ vị),the "blur quality". This is derived as a noun form of the verbbokeru,which is written in several ways,with additional meanings and nuances:Vựng けるrefers to being blurry, hazy or out-of-focus, whereas theHốt けるandNgốc けるspellings refer to being mentally hazy, befuddled, childish, senile, or playing stupid.Jisaboke(Thời soa ボケ)(literally, "time difference fog" ) is the term for jet lag.Nebokeru(Tẩm ぼける)is a verb denoting the actions or condition of someone who is half-asleep, or nodding off.Tobokerumeans playing dumb, andtoboketa kaorefers to a poker face. The related termbokashi(Vựng かし)means intentional blurring or gradation; that is a noun form of the transitive verbbokasu(Vựng す),which means to make something blurry, rather than to be blurry.

Use abroad

The English spellingbokehwas popularized in 1997 inPhoto Techniquesmagazine, 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".

The spellingsbokehandbokehave both been in use since at least 1996, when Merklinger had suggested "or Bokeh if you prefer."The termbokehhas appeared in photography books as early as 1998. It is sometimes pronounced/ˈboʊkə/BOH-kə.

Bokeh and lens design

Thedepth of fieldis the region where the size of thecircle of confusionis less than the resolution of the human eye.

Though difficult to quantify, some lenses have subjectively more pleasing out-of-focus areas. "Good" bokeh is especially important formacro lensesand longtelephoto lenses,because they are typically used in situations that produce shallowdepth of field.Good bokeh is also important for medium telephoto lenses (typically 85–150 mm on 35 mm format). 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.

Bokeh characteristics may be quantified by examining the image'scircle 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 on how a lens is corrected forspherical aberration,the disc may be uniformly illuminated, brighter near the edge, or brighter near the center. A well-known lens that exhibited the latter "soap-bubble" characteristic was that produced by Hugo Meyer & Co., more recently revived byMeyer Optik Görlitz.

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. The shape of the aperture has an influence on the subjective quality of bokeh as well. For conventional lens designs (with bladed apertures), when a lens is stopped down smaller than its maximumaperturesize (minimumf-number), out-of-focus points are blurred into thepolygonalshape 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 a polygon. Minolta has been on the forefront of promoting and introducing lenses with near-ideal circular apertures since 1987, but most other manufacturers now offer lenses with shape-optimized diaphragms, at least for the domain of portraiture photography. In contrast, acatadioptrictelephoto lensrenders bokehs resembling doughnuts, because itssecondary mirrorblocks 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.

Lenses with 11, 12, or 15 blade iris diaphragms are often claimed to excel in bokeh quality. Because of this, the lenses do not need to reach wide apertures to get better circles (instead of polygons). 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. Leica could reach a good bokeh at f/4.5. Today it is much easier to make an f/1.8 lens, and a 9-bladed lens at f/1.8 is enough for an 85 mm lens to achieve great bokeh.

Some lens manufacturers includingNikon,Minolta,andSonymake lenses designed with specific controls to change the rendering of the out-of-focus areas.

The Nikon 105 mm DC-Nikkorand 135 mm DC-Nikkorlenses (DC stands for "Defocus Control" ) have a control ring that permits the overcorrection or undercorrection ofspherical aberrationto change the bokeh in front of and behind thefocal plane.

TheMinolta/Sony STF 135 mm f/2.8 [T4.5](with STF standing forsmooth trans focus) is a lens specifically designed to produce pleasing bokeh. It is possible to choose between two diaphragms: one with 9 and another with 10 blades. Anapodizationfilter is used to soften the aperture edges which results in a smooth defocused area with gradually fading circles. Those qualities made it the only lens of this kind on the market from its introduction in 1999 to 2014. In 2014Fujifilmannounced a lens utilizing a similar apodization filter in theFujinon XF 56mm F1.2 R APD lens.Sony added theSony FE 100 mm F2.8 STF GM OSSin 2017.

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. It can be re-purposed for defocus control.

In 2015,Meyer Optik USA Inc.launched aKickstartercampaign to produce the Trioplan f2.9/50, a new lens based on one originally produced by Hugo Meyer & Co.; both lenses exhibit a characteristic "soap-bubble" bokeh.

The use ofanamorphiclenses will cause bokeh to appear differently along the horizontal and vertical axes of the lens, becoming ellipsoidal compared to those in a spherical lens.

In 2016,Apple Inc.released theiPhone 7 Pluswhich can take pictures with "Portrait Mode" (a bokeh like effect).Samsung'sGalaxy Note 8has a similar effect available. Both of these phones use dual cameras to detect edges and create a "depth map" of the image, which the phone uses to blur the out-of-focus portions of the photo. Other phones, like theGoogle Pixel,only use a single camera and machine learning to create the depth map.

In 2017,Vivoreleased a smartphone with dual front lenses forselfieswith bokeh. The first, a 20 MP lens, uses a 1/2.78 "sensor with f/2.0 aperture, while the second, an 8 MP f/2.0 lens, captures depth information. Bokeh can be made with a combination of both lenses, and shots can be refocused even after they are captured, adding bokeh effects with different depths.

In early 2018, theHonor9 Lite smartphone was released with quad cameras (two dual-lens). Both the front and back cameras have a 13 MP main lens and a 2 MP lens for capturing bokeh depth information.

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  An extremely shallowdepth of field,a common effect inmacrophotography,emphasizes bokeh.
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  200 mm lens atf/2.
• Catadioptric lensbokeh in motion.
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  The bokeh produced by acatadioptric lens(also called a mirror lens).
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  An example of the bokeh produced by the Canon 85 mm prime f/1.8 lens. The polygonal shapes are due to the 8-bladed aperture diaphragm being slightly closed. At its full aperture (f/1.8) these shapes would be smooth and not polygonal.
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  Catadioptric lensbokeh seen in more detail.
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  An example of the creative application of bokeh.
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  An example of the bokeh produced by the Canon 18–55 mm f/3.5–5.6 IS II lens.
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  A bokeh created with Nikon D3300 Camera 18–55 mm f/3.5–5.6 G VR II Lens.
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  Subtle swirly bokeh in the background
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  Swirly bokeh
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  Picture ofForsythiawith doughnut-shaped background bokeh, due to the use of a catadioptric system. Focus on foreground.
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  Picture ofForsythiawith doughnut-shaped foreground bokeh, due to the use of a catadioptric system. Focus on background
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  Silicon Valleybackground/bokeh shot withSamsung Galaxy S22Ultra smartphone
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  Bokeh created by theSamsung Galaxy A54's main camera

Emulation

From left to right: an original photo with no bokeh or blur; the same photo with synthetic bokeh effect applied to its background; the same photo withGaussian blurapplied to its background

Bokeh can be simulated byconvolvingthe image with akernelthat 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.Also, bokeh is not just any blur. To a first approximation, defocus blur is convolution by a uniformdisk,a more computationally intensive operation than the "standard"Gaussian blur;the former produces sharp circles around highlights whereas the latter is a much softer effect.Diffractionmay alter the effective shape of the blur. Some graphics editors have a filter to do this, usually called "Lens Blur".Accurate bokeh simulation requires running the blur in linear, HDR space. For low dynamic range images, anartificial neural networkmay be used to reconstruct the HDR light.

An alternative mechanical mechanism has been proposed for generating bokeh in small aperture cameras such as compacts or cellphone cameras, called image destabilisation,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.

Some advanced digital cameras have bokeh features which take several images with different apertures and focuses and then manually compose them afterward to one image. More advanced systems of bokeh use a hardware system of 2 sensors, one sensor to take photo as usual while other ones record depth information. Bokeh effect and refocusing can then be applied to an image after the photo is taken.

Other applications

In 2009,a research group atMIT Media Labshowed that the bokeh effect can be used to make imperceptibly small barcodes, orbokodes.By using barcodes as small as 3 mm with a small lens over them, if the barcode is viewed out of focus through an ordinary camera focused at infinity, the resulting image is large enough to scan the information in the barcode.

See also

• Airy disk
• Light-field camera
• Mandelbaum effect
• Orb (optics)
• Soft focus
• Special effect

External links

• Tool allowing to compare background blur of different lenses and camerasArchived2020-07-29 at theWayback Machine