View source for Physics:Bokeh

{{short description|Aesthetic quality of blur in the out-of-focus parts of an image}}
[[Image:Josefina with Bokeh.jpg|thumb|Coarse bokeh on a photo shot with an 85&nbsp;mm lens and 70&nbsp;mm [[Physics:Entrance pupil|entrance pupil]] diameter, which corresponds to {{f/}}1.2]]
[[File:Katherine Maher.jpg|thumb|right|An example of a portrait photo (of Katherine Maher). Note the 'swirly' bokeh.]]
[[File:Aperture_and_bokeh.jpg|thumb|How the bokeh varies with the aperture.]]

In [[Photography|photography]], '''bokeh''' ({{IPAc-en|ˈ|b|oʊ|k|ə}} {{respell|BOH|kə}} or {{IPAc-en|ˈ|b|oʊ|k|eɪ}} {{respell|BOH|kay}};<ref>{{Citation|last=Nikon|title=Bokeh for Beginners|date=2017-03-30|url=https://www.nikonusa.com/en/learn-and-explore/a/tips-and-techniques/bokeh-for-beginners.html|access-date=2019-07-24|archive-date=2019-07-24 |archive-url=https://web.archive.org/web/20190724152154/https://www.nikonusa.com/en/learn-and-explore/a/tips-and-techniques/bokeh-for-beginners.html|url-status=live}}</ref> {{IPA-ja|boke|lang}}) is the aesthetic quality of the blur produced in [[Physics:Defocus aberration|out-of-focus]] parts of an image, caused by [[Physics:Circle of confusion|circles of confusion]].<ref name="Gerry Kopelow 1998 118–119">{{cite book
 | title = How to photograph buildings and interiors
 | edition = 2nd
 | author = Gerry Kopelow
 | publisher = Princeton Architectural Press
 | year = 1998
 | isbn = 978-1-56898-097-3
 | pages = [https://archive.org/details/howtophotographb0000kope/page/118 118]–119
 | url = https://archive.org/details/howtophotographb0000kope
 | url-access = registration
 | quote = bokeh focus.
 }}</ref><ref>
{{cite book
 | title = Hollywood Portraits: Classic Shots and How to Take Them
 | author = Roger Hicks and Christopher Nisperos
 | publisher = Amphoto Books
 | year = 2000
 | isbn = 978-0-8174-4020-6
 | page = 132
 | url = https://books.google.com/books?id=7GfsKp7StwcC&q=bokeh+focus&pg=PA132
 }}</ref><ref>
{{cite book
 | title = Dictionary of Photography and Digital Imaging: The Essential Reference for the Modern Photographer
 | author = Tom Ang
 | publisher = Watson–Guptill
 | isbn = 0-8174-3789-4
 | year = 2002
 | url = https://books.google.com/books?id=fu3akyrFZEMC&q=bokeh+focus&pg=PA45}}</ref> Bokeh has also been defined as "the way the [[Physics:Lens|lens]] renders out-of-focus points of light".<ref>{{cite web
 | url = http://photojpn.org/words/len.html
 | title = PhotoWords/Lens
 | work = PhotoGuide Japan
 | access-date = 2009-10-30 
 | archive-date = 2018-12-26 
 | archive-url = https://web.archive.org/web/20181226094251/http://photojpn.org/words/len.html
 | url-status = live
 }}</ref> Differences in [[Physics:Optical aberration|lens aberrations]] and [[Astronomy:Aperture|aperture]] shape cause very different bokeh effects.<ref name="davis" /> 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).<ref name=davis>
{{cite book
 | title = Practical Artistry: Light & Exposure for Digital Photographers
 | author = Harold Davis
 | publisher = O'Reilly Media
 | year = 2008
 | isbn = 978-0-596-52988-8
 | page = 62
 | url = https://books.google.com/books?id=ZkOYrPiIwFIC&q=bokeh+good+bad&pg=PA62
 }}</ref> Photographers may deliberately use a [[Shallow focus|shallow focus]] technique to create images with prominent out-of-focus regions, accentuating their lens's bokeh.

Bokeh is often most visible around small background [[Physics:Point source#Light|highlights]], such as [[Physics:Specular reflection|specular reflection]]s and [[Physics:List of light sources|light sources]], which is why it is often associated with such areas.<ref name=davis/> However, bokeh is not limited to highlights; blur occurs in all regions of an image which are outside the [[Depth of field|depth of field]].

The opposite of bokeh—an image in which multiple distances are visible and all are in focus—is [[Deep focus|deep focus]].

==Etymology==
The term comes from the [[Social:Japanese language|Japanese]] word {{nihongo||暈け/ボケ|boke}}, which means "blur" or "haze", resulting in {{Nihongo||ボケ味|boke-aji}}, the "blur quality". This is derived as a noun form of the verb {{transl|ja|bokeru}}, which is written in several ways,<ref name="wwwjdic-bokeru">{{cite web | url = https://www.edrdg.org/cgi-bin/wwwjdic/wwwjdic?1MDJ%CA%F2%A4%B1%A4%EB | title = wwwjdic: bokeru entry | access-date = 2020-03-04  | archive-date = 2021-03-08  | archive-url = https://web.archive.org/web/20210308084448/https://www.edrdg.org/cgi-bin/wwwjdic/wwwjdic?1MDJ%CA%F2%A4%B1%A4%EB | url-status = live }}</ref> with additional meanings and nuances: {{Nihongo2|暈ける}} refers to being blurry, hazy or out-of-focus, whereas the {{Nihongo2|惚ける}} and {{Nihongo2|呆ける}} spellings refer to being mentally hazy, befuddled, childish, senile, or playing stupid. {{Nihongo||時差ボケ|Jisaboke}}<ref>{{cite web | url = https://www.edrdg.org/cgi-bin/wwwjdic/wwwjdic?1MDJ%BB%FE%BA%B9%A5%DC%A5%B1 | title = wwwjdic: jisaboke entry | access-date = 2020-03-04  | archive-date = 2021-03-08  | archive-url = https://web.archive.org/web/20210308030352/https://www.edrdg.org/cgi-bin/wwwjdic/wwwjdic?1MDJ%BB%FE%BA%B9%A5%DC%A5%B1 | url-status = live }}</ref> (literally, "time difference fog") is the term for jet lag. {{Nihongo||寝ぼける|Nebokeru}}<ref>{{cite web | url = https://www.edrdg.org/cgi-bin/wwwjdic/wwwjdic?1MDJ%A4%CD%A4%DC%A4%B1%A4%EB | title = wwwjdic: nebokeru entry | access-date = 2020-03-04  | archive-date = 2021-03-08  | archive-url = https://web.archive.org/web/20210308073325/https://www.edrdg.org/cgi-bin/wwwjdic/wwwjdic?1MDJ%A4%CD%A4%DC%A4%B1%A4%EB | url-status = live }}</ref> is a verb denoting the actions or condition of someone who is half-asleep, or nodding off. {{transl|ja|Tobokeru}}<ref>{{cite web | url = https://www.edrdg.org/cgi-bin/wwwjdic/wwwjdic?1MDJ%A4%C8%A4%DC%A4%B1%A4%EB | title = wwwjdic: tobokeru entry | access-date = 2020-03-04  | archive-date = 2021-03-08  | archive-url = https://web.archive.org/web/20210308203738/https://www.edrdg.org/cgi-bin/wwwjdic/wwwjdic?1MDJ%A4%C8%A4%DC%A4%B1%A4%EB | url-status = live }}</ref> means playing dumb, and {{transl|ja|toboketa kao}} refers to a poker face. The related term {{Nihongo||暈かし|bokashi}} means intentional blurring or gradation; that is a noun form of the transitive verb {{Nihongo||暈す|bokasu}}, which means to make something blurry, rather than to be blurry.

===Use abroad===
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".<ref name=johnston>{{cite web
 | author = Johnston, Mike
 | date = April 4, 2004
 | url = http://www.luminous-landscape.com/columns/sm-04-04-04.shtml
 | title = The Sunday Morning Photographer, 2004: Bokeh in Pictures
 | publisher = luminous-landscape.com
 | access-date = July 3, 2009
 | archive-url = https://web.archive.org/web/20150103180320/http://www.luminous-landscape.com/columns/sm-04-04-04.shtml
 | archive-date = 3 January 2015
 | url-status = dead
 }}</ref>

The spellings ''bokeh'' and ''boke'' have both been in use since at least 1996, when Merklinger had suggested "or Bokeh if you prefer."<ref>{{cite web
 | author = Merklinger, Harold
 | url = http://www.luminous-landscape.com/essays/bokeh.shtml
 | title = Understanding Boke
 | publisher = luminous-landscape.com
 | access-date = July 3, 2009
 | archive-url = https://web.archive.org/web/20130409135024/http://www.luminous-landscape.com/essays/bokeh.shtml
 | archive-date = 9 April 2013
 | url-status = dead
 }}</ref> The term ''bokeh'' has appeared in photography books as early as 1998.<ref name="Gerry Kopelow 1998 118–119"/>
It is sometimes pronounced {{IPAc-en|ˈ|b|oʊ|k|ə}} {{respell|BOH|kə}}.<ref name="Wes McDermott 2009 198">{{cite book|url=https://books.google.com/books?id=4CAlJgUyEs0C&q=bokeh+boke-uh&pg=PA198|title=Real World Modo: The Authorized Guide: In the Trenches with Modo|author=Wes McDermott|publisher=Focal Press|year=2009|isbn=978-0-240-81199-4|page=198}}</ref>

===Use in video===
The background blur ''bokeh'' effect is harder to achieve using digital video cameras than with standard photography, but can still be achieved by having the background further behind the subject of the video, and this additional space may be required to achieve this result than with photography.{{why|reason=source gives no explanation|date=March 2023}}<ref>{{Cite web|date=2023-01-12|title=9 Helpful Tips for Choosing Corporate Video Locations|url=https://vermillionfilms.com/corporate-video-location-guide/|access-date=2023-03-01|website=Vermillion Films|language=en-GB|archive-date=2023-03-01 |archive-url=https://web.archive.org/web/20230301112354/https://vermillionfilms.com/corporate-video-location-guide/|url-status=live}}</ref>

==Bokeh and lens design==
[[Image:Circles of confusion lens diagram.svg|thumb|right|280px|The [[Depth of field|depth of field]] is the region where the size of the circle of confusion is 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 for macro lenses and long [[Engineering:Telephoto lens|telephoto lens]]es, because they are typically used in situations that produce shallow [[Depth of field|depth 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's [[Physics:Circle of confusion|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 on how a lens is corrected for [[Physics:Spherical aberration|spherical 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 by [[Company:Meyer Optik Görlitz|Meyer Optik Görlitz]].<ref>{{cite web|url=http://www.meyer-optik-goerlitz.com/how-to-create-soap-bubble-bokeh/|author=Blog|title=How to Create Soap Bubble Bokeh|access-date=3 August 2016|archive-url=https://web.archive.org/web/20160725193816/http://www.meyer-optik-goerlitz.com/how-to-create-soap-bubble-bokeh/|archive-date=25 July 2016|url-status=dead}}</ref>

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.<ref>{{cite web|url=http://www.bhphotovideo.com/explora/photography/tips-and-solutions/understanding-bokeh/|author=Todd Vorenkamp|title=Understanding Bokeh|access-date=2016-08-03 |archive-date=2016-05-27 |archive-url=https://web.archive.org/web/20160527165827/http://www.bhphotovideo.com/explora/photography/tips-and-solutions/understanding-bokeh|url-status=live}}</ref> 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 maximum [[Astronomy:Aperture|aperture]] size (minimum [[F-number|f-number]]), out-of-focus points are blurred into the [[Polygon|polygon]]al 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 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, a [[Astronomy:Catadioptric system|catadioptric]] [[Engineering:Telephoto lens|telephoto lens]] renders bokehs resembling doughnuts, because its [[Astronomy:Secondary mirror|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.<ref>{{cite web|url=http://www.diyphotography.net/diy_create_your_own_bokeh|author=Karsten Stroemvig|title=DIY — Create your own Bokeh|date=25 April 2007|access-date=2009-11-18 |archive-date=2009-12-07 |archive-url=https://web.archive.org/web/20091207203943/http://www.diyphotography.net/diy_create_your_own_bokeh|url-status=live}}</ref>

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 85mm lens to achieve great bokeh.

Some lens manufacturers including [[Company:Nikon|Nikon]],<ref>{{cite web|url=http://www.europe-nikon.com/en_GB/product/nikkor-lenses/auto-focus-lenses/fx/single-focal-length/af-dc-nikkor-135mm-f-2d|title=AF DC-Nikkor 135mm f/2D Single Focal Length FX Auto Focus Lenses NIKKOR Lenses|work=europe-nikon.com|access-date=2015-05-01|archive-date=2016-03-05 |archive-url=https://web.archive.org/web/20160305190546/http://www.europe-nikon.com/en_GB/product/nikkor-lenses/auto-focus-lenses/fx/single-focal-length/af-dc-nikkor-135mm-f-2d|url-status=live}}</ref> Minolta, and Sony make lenses designed with specific controls to change the rendering of the out-of-focus areas.

The Nikon 105 mm DC-Nikkor<ref>{{cite web|url=http://www.nikonusa.com/en/Nikon-Products/Product/Camera-Lenses/1932/af-dc-nikkor-105mm-f%252F2D.html|title=AF DC-NIKKOR 105mm f/2D from Nikon|access-date=2013-10-29 |archive-date=2013-10-20 |archive-url=https://web.archive.org/web/20131020154937/http://www.nikonusa.com/en/Nikon-Products/Product/Camera-Lenses/1932/AF-DC-NIKKOR-105mm-f/2D.html|url-status=live}}</ref> and 135&nbsp;mm DC-Nikkor<ref>{{cite web|url=http://www.nikonusa.com/en/Nikon-Products/Product/Camera-Lenses/1935/AF-DC-Nikkor-135mm-f%252F2D.html|title=AF DC-NIKKOR 135&nbsp;mm f/2D from Nikon|access-date=2013-10-29 |archive-date=2013-10-20 |archive-url=https://web.archive.org/web/20131020201703/http://www.nikonusa.com/en/Nikon-Products/Product/Camera-Lenses/1935/af-dc-nikkor-135mm-f/2D.html|url-status=live}}</ref> lenses (DC stands for "Defocus Control") have a control ring that permits the overcorrection or undercorrection of [[Physics:Spherical aberration|spherical aberration]] to change the bokeh in front of and behind the [[Physics:Cardinal point (optics)|focal plane]].

The Minolta/Sony STF 135&nbsp;mm f/2.8 [T4.5] (with STF standing for ''smooth 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. An [[Apodization|apodization]] filter 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 2014 [[Company:Fujifilm|Fujifilm]] announced a lens utilizing a similar apodization filter in the Fujinon XF 56mm F1.2 R APD lens.<ref>{{cite web|title=Fujifilm introduces XF 56mm F1.2 R APD with apodization filter|url=http://www.dpreview.com/articles/4106200256/fujifilm-introduces-xf-56mm-f1-2-r-apd-with-apodization-filter|website=DPReview|access-date=2015-05-16 |archive-date=2015-05-31 |archive-url=https://web.archive.org/web/20150531092545/http://www.dpreview.com/articles/4106200256/fujifilm-introduces-xf-56mm-f1-2-r-apd-with-apodization-filter|url-status=live}}</ref> Sony added the Sony FE 100&nbsp;mm F2.8 STF GM OSS in 2017.<ref>{{cite web |title=Neu von Sony: E-Mount-Objektive 100 mm F2.8 STF GM, FE 85 mm F1.8; Blitz HVL-F45RM |date=2017-02-07 |language=de |work=Photoscala |url=http://www.photoscala.de/2017/02/07/neu-von-sony-e-mount-objektive-100-mm-f2-8-stf-gm-fe-85-mm-f1-8-blitz-hvl-f45rm/ |access-date=2017-02-10 |url-status=live |archive-url=https://web.archive.org/web/20170211003316/http://www.photoscala.de/2017/02/07/neu-von-sony-e-mount-objektive-100-mm-f2-8-stf-gm-fe-85-mm-f1-8-blitz-hvl-f45rm/ |archive-date=2017-02-11}}</ref>

The 'Sigma YS System Focusing' 135&nbsp;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.
<ref>{{cite web|url=http://www.4photos.de/test/Bokeh-Defocus-Control.html|author=Markus Keinath|title=Cheap DC Nikkor Substitute|access-date=2013-10-29 |archive-date=2013-10-14 |archive-url=https://web.archive.org/web/20131014164035/http://www.4photos.de/test/Bokeh-Defocus-Control.html|url-status=live}}</ref>

In 2015, [[Company:Meyer Optik Görlitz|Meyer Optik USA Inc.]] launched a Kickstarter campaign 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.<ref>{{cite web|url=http://en.globell.com/Meyer-Optik-brings-back-legendary-Trioplan-f2.8-100-soap-bubble-bokeh-lens-with-Kickstarter-campai_detail_968_2236.html|author=Meyer-Optik-Görlitz / net SE|title=Meyer Optik brings back legendary Trioplan f2.8/100 'soap bubble' bokeh lens with Kickstarter campaign|access-date=2016-08-03|archive-url=https://web.archive.org/web/20160818100516/http://en.globell.com/Meyer-Optik-brings-back-legendary-Trioplan-f2.8-100-soap-bubble-bokeh-lens-with-Kickstarter-campai_detail_968_2236.html|archive-date=2016-08-18|url-status=dead}}</ref>

The use of anamorphic lenses 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, [[Company:Apple Inc.|Apple Inc.]] released the [[Engineering:IPhone 7 Plus|iPhone 7 Plus]] which can take pictures with "Portrait Mode" (a bokeh like effect).<ref>{{Cite news|url=https://petapixel.com/2016/10/24/apple-just-released-fake-bokeh-portrait-mode-everyone/|title=Apple Just Released Their Fake Bokeh Portrait Mode to Everyone|date=2016-10-24|work=PetaPixel|access-date=2017-11-28|language=en-US|archive-date=2017-12-12 |archive-url=https://web.archive.org/web/20171212190031/https://petapixel.com/2016/10/24/apple-just-released-fake-bokeh-portrait-mode-everyone/|url-status=live}}</ref> Samsung's Galaxy Note 8 has 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 the [[Software:Google Pixel|Google Pixel]], only use a single camera and machine learning to create the depth map.<ref name="How Portrait Mode Works">{{cite web |last1=Simpson |first1=Jayphen |title=How Portrait Mode Works and How It Compares to an $8,000 Camera |url=https://petapixel.com/2017/12/11/portrait-mode-works-compares-8000-camera/ |website=PetaPixel |access-date=11 December 2017 |date=11 December 2017 |archive-date=2018-06-04  |archive-url=https://web.archive.org/web/20180604233929/https://petapixel.com/2017/12/11/portrait-mode-works-compares-8000-camera/ |url-status=live }}</ref>

In 2017, Vivo released a smartphone with dual front lenses for [[Philosophy:Selfie|selfies]] with 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.<ref>{{cite web |url=http://www.gsmarena.com/vivo_v5_plus_becomes_official_with_dual_front_camera_snapdragon_625-news-22831.php |title=vivo V5 Plus becomes official with dual front camera, Snapdragon 625 |date=January 18, 2017 |access-date=2017-02-07  |archive-date=2017-02-08  |archive-url=https://web.archive.org/web/20170208033207/http://www.gsmarena.com/vivo_v5_plus_becomes_official_with_dual_front_camera_snapdragon_625-news-22831.php |url-status=live }}</ref>

In early 2018, the [[Software:Honor (brand)|Honor]] 9 Lite smartphone was released with quad cameras (two dual-lens). Both the front and back cameras have a 13MP main lens and a 2MP lens for capturing bokeh depth information.<ref>{{cite web |url=https://www.androidauthority.com/honor-9-lite-review-830795/ |title=Honor 9 Lite review: four lenses on a budget |author=ABHISHEK BAXI |access-date=March 30, 2018 |date=February 8, 2018 |archive-date=2018-03-30  |archive-url=https://web.archive.org/web/20180330143853/https://www.androidauthority.com/honor-9-lite-review-830795/ |url-status=live }}</ref>

<gallery widths="220" heights="160">
File:DOF-ShallowDepthofField.jpg|An extremely shallow [[Depth of field|depth of field]], a common effect in macrophotography, emphasizes bokeh.
File:Thumbs up for bokeh.JPG|200 mm lens at [[F-number|f/2]].
File:Catadioptric lens bokeh etc - 2018 12 08.webm|[[Astronomy:Catadioptric system|Catadioptric lens]] bokeh in motion.
File:Bahnhof Dortmund Brackel Spiegeltele DSC02359 smial wp.jpg|The bokeh produced by a [[Astronomy:Catadioptric system|catadioptric lens]] (also called a mirror lens).
File:Bokeh Example.jpg|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-number|f/1.8]]) these shapes would be smooth and not polygonal.
File:Donut bokeh.jpg|[[Astronomy:Catadioptric system|Catadioptric lens]] bokeh seen in more detail.
File:Christmas Tree Lights Bokeh.jpg|An example of the creative application of bokeh.
File:Bokeh.JPG|An example of the bokeh produced by the Canon 18–55mm f/3.5-5.6 IS II lens.
File:Bokeh1 DSC 0959.jpg|A bokeh created with Nikon D3300 Camera 18-55mm f/3.5-5.6 G VR II Lens.
File:Photography by Victor Albert Grigas (1919-2017) 000172050002 (37159721864).jpg|Subtle swirly bokeh in the background
File:Christmas Tree out of focus copy.jpg|Swirly bokeh
File:Bad Bokeh Background.jpg|Picture of ''[[Biology:Forsythia|Forsythia]]'' with doughnut-shaped background bokeh, due to the use of a catadioptric system. Focus on foreground.
File:Bad Bokeh 02.jpg|Picture of ''[[Biology:Forsythia|Forsythia]]'' with doughnut-shaped foreground bokeh, due to the use of a catadioptric system. Focus on background
File:Silicon Valley background Samsung Galaxy S22 Ultra.jpg|Silicon Valley background/bokeh shot with [[Engineering:Samsung Galaxy S22|Samsung Galaxy S22]] Ultra smartphone
File:Out of focus.png|alt=Bokeh on a cherry tree's leaves created by the Samsung Galaxy A54's main camera|Bokeh created by the [[Engineering:Samsung Galaxy A54 5G|Samsung Galaxy A54]]'s main camera
</gallery>

==Emulation==
[[Image:Faux-bokeh-comparison.jpg|thumb|upright=1.4|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 with [[Gaussian blur|Gaussian blur]] applied to its background]]

Bokeh can be simulated by [[Convolution|convolving]] the image with a [[Integral transform|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&nbsp;– at least in principle&nbsp;– has to include image points that are occluded by objects in the foreground.<ref>
{{Citation
 | last1 = Potmesil
 | first1 = M.
 | last2 = Chakravarty
 | first2 = I.
 | year = 1982
 | title = Synthetic Image Generation with a Lens and Aperture Camera Model
 | series = ACM Transactions on Graphics
 | publisher = ACM
 | volume = 1
 | issue = 2 (1982)
 | pages = 85–108
 | url = http://portal.acm.org/citation.cfm?id=357299.357300
 | issn = 0730-0301
 | doi = 10.1145/357299.357300
| s2cid = 9253049
 | doi-access = free
 }}
</ref> Also, bokeh is not just any blur. To a first approximation, defocus blur is convolution by a uniform [[Disk (mathematics)|disk]], 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. [[Physics:Diffraction|Diffraction]] may alter the effective shape of the blur. Some graphics editors have a filter to do this, usually called "Lens Blur".<ref>{{cite web|url=http://livedocs.adobe.com/en_US/Photoshop//10.0/help.html?content=WSA75837E3-FE05-4f86-A9DF-3C0DD602CA63.html|author=Adobe Photoshop CS3 Livedocs|title=Add lens blur|access-date=2014-05-23|archive-url=https://web.archive.org/web/20140523225356/http://livedocs.adobe.com/en_US/Photoshop//10.0/help.html?content=WSA75837E3-FE05-4f86-A9DF-3C0DD602CA63.html|archive-date=2014-05-23|url-status=dead}}</ref> Accurate bokeh simulation requires running the blur in linear, HDR space. For low dynamic range images, a [[Neural network|neural network]] may be used to reconstruct the HDR light.<ref>{{cite arXiv |last1=Zhang |first1=Xuaner |last2=Matzen |first2=Kevin |last3=Nguyen |first3=Vivien |last4=Yao |first4=Dillon |last5=Zhang |first5=You |last6=Ng |first6=Ren |title=Synthetic Defocus and Look-Ahead Autofocus for Casual Videography |date=21 May 2019|class=cs.CV |eprint=1905.06326 }} [https://ceciliavision.github.io/vid-auto-focus/ SIGGRAPH 2019 project page] {{Webarchive|url=https://web.archive.org/web/20230324073704/https://ceciliavision.github.io/vid-auto-focus/ |date=2023-03-24  }}</ref> 

An alternative mechanical mechanism has been proposed for generating bokeh in small aperture cameras such as compacts or cellphone cameras, called image destabilisation,<ref>{{cite web |url=https://www.newscientist.com/article/mg20427346.700-nextgeneration-cameras-bring-photography-tricks-to-the-masses.html |first=Jim |last=Giles |work=New Scientist (Subscription required) |title=Next-generation cameras bring photography tricks to the masses |access-date=2011-04-04 |archive-date=2011-11-14  |archive-url=https://web.archive.org/web/20111114015051/http://www.newscientist.com/article/mg20427346.700-nextgeneration-cameras-bring-photography-tricks-to-the-masses.html |url-status=live }}</ref><ref>{{cite web|url=http://web.media.mit.edu/~ankit/id/|author=Ankit Mohan and Douglas Lanman and Shinsaku Hiura and Ramesh Raskar|title=Image Destabilization: Programmable Defocus using Lens and Sensor Motion|url-status=dead|archive-url=https://web.archive.org/web/20090924193620/http://web.media.mit.edu/~ankit/id/|archive-date=2009-09-24}}</ref> 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.<ref>{{cite news |url=http://connect.dpreview.com/post/9386067747/htc-launches-one-m8 |title=HTC launches One M8 with new 'Duo Camera' |author=Lars Rehm |newspaper=Dpreview |date=March 25, 2014 |access-date=2014-03-27  |archive-date=2015-10-03  |archive-url=https://web.archive.org/web/20151003195918/http://connect.dpreview.com/post/9386067747/htc-launches-one-m8 |url-status=live }}</ref>

==Other applications==
In 2009,<ref>{{cite web |last=Fildes |first=Jonathan |url=http://news.bbc.co.uk/1/hi/technology/8170027.stm |title=Barcode replacement shown off |work=BBC News |date=2009-07-27 |access-date=2012-02-19 |archive-date=2022-12-07  |archive-url=https://web.archive.org/web/20221207051739/http://news.bbc.co.uk/1/hi/technology/8170027.stm |url-status=live }}</ref> a research group at [[Organization:MIT Media Lab|MIT Media Lab]] showed that the bokeh effect can be used to make imperceptibly small barcodes, or [[Bokode|bokode]]s. By using barcodes as small as 3&nbsp;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.<ref>Mohan, A., Woo, G, Hiura, S, Smithwick, Q, Raskar, R. [http://web.media.mit.edu/~ankit/bokode/ Bokode: Imperceptible Visual Tags for Camera Based Interaction from a Distance] {{webarchive |url=https://web.archive.org/web/20090730073705/http://web.media.mit.edu/~ankit/bokode/ |date=July 30, 2009 }}. ACM SIGGRAPH 2009.</ref>

==See also==
*Aberration in optical systems
*[[Physics:Airy disk|Airy disk]]
*[[Engineering:Anamorphic format|Anamorphic format]]
*[[Physics:Circle of confusion|Circle of confusion]]
*[[Depth of field]]
*[[Engineering:Light-field camera|Light-field camera]]
*[[Physics:Mandelbaum effect|Mandelbaum effect]]
*Orb (optics)
*[[Soft focus]]
*[[Special effect]]

==References==
{{reflist}}

==External links==
*[https://howmuchblur.com/#lens-1x-50mm-f1.4-vs-1x-85mm-f1.8-on-0.9m-subject Tool allowing to compare background blur of different lenses and cameras] {{Webarchive|url=https://web.archive.org/web/20200729130820/https://www.howmuchblur.com/#lens-1x-50mm-f1.4-vs-1x-85mm-f1.8-on-0.9m-subject |date=2020-07-29  }}

{{Photography}}

[[Category:Science of photography]]

{{Sourceattribution|Bokeh}}