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Bokeh

Bokeh is a photographic effect referring to the aesthetic of the produced in the out-of-focus parts of an image, particularly the way lenses render highlights and points of light as soft, circular or polygonal shapes. The term originates from the word boke (暈け or ぼけ), meaning "" or "haze," and was introduced to Western in the to describe this visually pleasing defocus rather than in general. Achieving desirable bokeh typically involves creating a shallow , which isolates the subject from the background. This is accomplished by using a wide (low , such as f/2.8 or lower), longer lenses (like 85mm or telephoto), and positioning the subject at a distance from background elements with specular highlights, such as lights or reflective surfaces. The character of bokeh—whether smooth and creamy or harsh and distracting—depends on factors like the number and shape of the lens's blades; rounded blades produce more circular, pleasing orbs, while straight-edged ones can yield hexagonal or polygonal shapes. Bokeh enhances visual appeal by drawing attention to the subject while softly blurring distractions, adding a sense of depth and artistic separation. High-quality bokeh is prized in lens design, with manufacturers like and Nikon optimizing for it, and it has influenced digital post-processing tools that simulate the effect in software like .

Definition and Fundamentals

Core Definition

Bokeh refers to the aesthetic quality of the out-of-focus blur in a , specifically the manner in which defocused elements, such as , are rendered by the . This effect is characterized by the soft, blurred rendition of highlights, which can appear as circular or polygonal shapes, contributing to the overall visual appeal of the image. Unlike general , which simply describes the lack of in an image, bokeh evaluates the subjective pleasingness or harshness of those out-of-focus regions, particularly in specular highlights like streetlights, holiday lights, or distant foliage. It emphasizes the character of the blur rather than its extent, often manifesting in smooth, creamy transitions that enhance without distracting from the subject. In typical examples, bokeh appears as round, glowing orbs or softly edged polygons in the background, helping to isolate the main subject by creating a of depth and separation. These shapes emerge in areas outside the , the zone where elements appear acceptably sharp.

Aesthetic Qualities

The aesthetic appeal of bokeh lies in its ability to create visually pleasing out-of-focus areas that enhance the subject's prominence without distracting from the . Good bokeh is characterized by smooth transitions between light and dark regions in the blurred areas, resulting in a soft, creamy appearance that guides the viewer's eye naturally toward the focal point. Rounded or oval highlight shapes further contribute to this desirability, avoiding any angular or harsh edges that could disrupt the image's harmony. Minimal onion-ring artifacts—concentric rings within bokeh highlights—are also a key criterion, as these imperfections can make the blur appear unnatural and detract from the overall elegance. In contrast, undesirable bokeh often exhibits nervous or busy patterns, where the out-of-focus elements form jagged, irregular shapes that create visual clutter and compete with the subject. Polygonal highlights, arising from the aperture's geometry, produce hard-edged, geometric forms that can appear and unappealing, especially in portraits or scenes with point light sources. Additionally, in complex backgrounds with intricate details, bokeh can become distractingly nervous, amplifying textures into a chaotic mosaic rather than a serene backdrop. Subjective factors play a significant role in bokeh's evaluation. For instance, lenses like the Canon RF 85mm f/1.2L produce creamy bokeh with uniform smoothness, ideal for clean, modern portraits, while options such as the Helios-44 yield swirly bokeh with swirling patterns around edges, adding a whimsical, artistic flair favored in creative or retro styles. These variations highlight how bokeh's desirability can shift based on intent, with creamy renders suiting minimalist and swirly ones enhancing dynamic compositions.

History and Etymology

Origins of the Concept

The recognition of in dates back to the , particularly in portraiture, where photographers began intentionally employing to evoke emotion and artistic depth. , a who started her career in at age 48, pioneered this approach with her close-up portraits of Victorian figures, using shallow and deliberate unfocused elements to create a hazy, dreamlike quality that mimicked . Her work, often featuring smeared lenses or slight camera movement, challenged the era's emphasis on technical sharpness and highlighted the expressive potential of out-of-focus areas. This early experimentation gained momentum in the Pictorialist movement, spanning the late 19th and early 20th centuries, as photographers sought to elevate the medium to status. Pictorialists like and deliberately incorporated , textured papers, and diffused lighting to produce atmospheric images that prioritized mood and composition over documentary precision, treating blurred regions as integral to the aesthetic narrative. The movement's influence extended into portraiture and genre scenes, where intentional blur isolated subjects and softened edges to convey or romance. Throughout the , prior to the 1990s, these principles evolved in through the use of large-format lenses, which provided exceptional control over shallow for subject isolation against blurred environments. Pioneers such as Baron Adolf de Meyer, working for in the 1910s and 1920s, applied soft-focus techniques with platinum prints and diffused light to craft ethereal, glamorous portraits that blurred backgrounds into impressionistic forms, setting a standard for commercial elegance. Later, in the mid-20th century employed 8x10-inch large-format cameras to manipulate precisely, rendering out-of-focus areas as smooth, tonal transitions that accentuated garment details and model poise in studio settings. A pivotal milestone came post-World War II with the advent of faster lenses, exemplified by Canon's 50mm f/1.2 lens introduced in , which allowed wide-open apertures to produce pronounced blur circles and minimal for creative subject separation. This innovation, building on wartime optical advancements, enabled photographers to exploit intentional out-of-focus effects in low-light conditions, further embedding blur as a tool for artistic emphasis in and genre work.

Development of the Term

The term "bokeh" derives from the Japanese word boke (ボケ), meaning "blur" or "haze," often connoting a mental fog or senility, and more precisely from boke-aji (ボケ味), which translates to "blur quality" or "blur taste," referring to the aesthetic character of out-of-focus areas in an image. This linguistic root emerged in Japanese photography contexts to describe the subjective appeal of blurred elements, distinct from mere technical defocus. In Japanese usage, boke-aji highlights the nuanced "flavor" of blur influenced by lens design. The term entered English-speaking circles in the through specialized magazines, with Mike Johnston, then editor of Photo Techniques, popularizing the spelling "bokeh" in the May/June 1997 issue after learning of it from photographers like Carl Weese. Johnston commissioned articles to introduce the , distinguishing it from generic "" to emphasize its artistic quality, thereby standardizing its adoption in Western discourse. This marked a shift from earlier informal descriptions of out-of-focus , as the term provided a precise, borrowed vocabulary for critiquing performance. By the 2000s, "bokeh" spread globally alongside the rise of digital single-lens reflex (SLR) cameras, which enabled photographers to experiment with shallow and share results online, turning it into a staple of photographic terminology. In non-English contexts, the term is generally retained as "bokeh," with pronunciation variations, in languages like , , and . Post-2010, the term's usage evolved in digital communities, with platforms amplifying discussions on bokeh emulation in imaging and post-processing, though early adoption focused on traditional .

Optical Principles

Depth of Field Mechanics

Depth of field (DoF) refers to the range of distances in object space over which an image appears acceptably sharp, typically defined by the distance between the nearest and farthest points where the blur, measured by the circle of confusion, remains below a specified threshold. This in-focus zone is influenced by several key optical factors: the aperture size, expressed as the f-number N; the focal length f of the lens; the subject distance u; and the sensor or film format size, which determines the allowable circle of confusion c. A wider aperture (smaller N) or longer focal length reduces DoF, as does focusing closer to the subject, while larger sensors generally yield shallower DoF for equivalent framing due to a proportionally larger c. The approximate formula for total DoF, valid when the subject distance u is much greater than the f and the is shallow relative to u (i.e., u \ll H), is given by: \text{DoF} \approx \frac{2 N c u^2}{f^2} Here, N is the (ratio of to diameter); c is the circle of confusion diameter, representing the maximum acceptable blur on the (often c \approx 0.03 mm for 35 mm format, scaled to diagonal); u is the distance from to subject; and f is the , all in consistent units (e.g., mm). This simplifies the DoF, which spans from near D_n = \frac{u H}{H + u} to far D_f = \frac{u H}{H - u}, where H = \frac{f^2}{N c} is the , by assuming u \ll H and neglecting higher-order terms. The derivation begins with the thin-lens equation, \frac{1}{f} = \frac{1}{u} + \frac{1}{[v](/page/V.)}, where [v](/page/V.) is the image distance, approximated as [v](/page/V.) \approx f for u \gg f. For a point offset by \Delta u from the focused subject, the corresponding image offset \Delta [v](/page/V.) \approx -\frac{[v](/page/V.)^2}{u^2} \Delta u due to longitudinal magnification \left(\frac{[v](/page/V.)}{u}\right)^2. The blur circle diameter at the image plane is then b \approx \frac{|\Delta [v](/page/V.)|}{N}, set equal to c for DoF limits. Solving for \Delta u yields \Delta u \approx \frac{N c u^2}{f^2}, so the total symmetric DoF is approximately twice this value. This geometric approach assumes paraxial rays and neglects aberrations or . In the context of bokeh, a shallow DoF—achieved primarily through wide (low N)—limits the in-focus range, rendering background and foreground elements out of and producing the blurred highlights characteristic of bokeh in those regions.

Blur Circle Formation

In optical , the point spread function () describes the spatial distribution of light from an ideal after passing through the system, resulting in a blurred disk known as the blur when the source is defocused. This blur arises because rays from the point converge not at the but offset due to the mismatch between the object's distance and the setting, spreading light over a circular area on the . The diameter of this blur is directly proportional to the diameter and the degree of defocus, with larger or greater distance from the plane producing wider circles that enhance the separation between in-focus and out-of-focus regions. The represents the maximum acceptable blur diameter on the beyond which a point is perceived as out of focus, serving as the threshold for sharpness in calculations. Technically, it is the region on the where rays from a defocused point intersect, and its size determines whether the blur exceeds the resolution limits of the or , typically on the order of a width for modern cameras. This concept underpins the transition from sharp to blurred rendering, where points within the acceptable contribute to the illusion of focus, while larger ones form visible defocus effects central to bokeh. In highlight rendering, bokeh balls emerge as the defocused projections of specular reflections or bright point sources, such as lights, transforming small, intense highlights into soft, rounded disks on the . These balls exhibit edge feathering due to the gradual falloff in the PSF, often approximating a Gaussian profile from and minor aberrations, which softens the boundaries and creates a smooth, non-abrupt transition from the highlight to the surrounding . The central of these bokeh balls remains high, reflecting the specular nature of the source, while the falloff ensures a pleasing, diffused appearance that emphasizes the aesthetic isolation of out-of-focus elements.

Lens Design and Bokeh

Aperture and Blade Influences

The shape and quality of bokeh are profoundly influenced by the construction of the , particularly the number and design of its blades in the iris diaphragm. Lenses with a higher number of blades, typically 9 or more, produce rounder out-of-focus highlights, resulting in smoother and more aesthetically pleasing bokeh, especially when the lens is stopped down from its maximum . In contrast, lenses with fewer blades, such as 5 or 6, often render bokeh as distinct polygons when not shot wide open, creating a more angular and sometimes harsher appearance in blurred areas. The shape of the blades themselves plays a critical role; rounded blades help approximate a circular , minimizing hard edges and enhancing bokeh smoothness, whereas straight blades accentuate polygonal forms. However, this effect is most noticeable in stopped-down scenarios and less so at wide apertures, where the blades retract fully, yielding circular bokeh regardless of count. Regarding diaphragm types, the —comprising overlapping curved metal leaves—dominates modern lens design and allows precise control over bokeh shape through blade count and curvature. Wide apertures, such as f/1.4, generate larger blur circles with inherently smoother bokeh by maximizing the out-of-focus area and minimizing blade visibility, while narrower settings like f/2.8 begin to reveal the aperture's polygonal influence, reducing bokeh size but potentially introducing shape artifacts if blades are few or straight. Historical lenses exemplify these principles; the 1930s Sonnar 50mm f/1.5 for rangefinders exhibited rough bokeh at wide apertures due to its era's optical design constraints, though it smoothed out when stopped down. This contrasts with contemporary lenses prioritizing rounded, high-blade-count for consistently circular bokeh across apertures.

Aberrations and Coatings

Lens aberrations significantly influence the quality of bokeh by introducing irregularities in the out-of-focus rendering, often resulting in unnatural or harsh blur patterns. , which occurs when rays passing through the periphery of a at a different point than those through the center, can lead to concentric "onion rings" visible within bokeh highlights, particularly in lenses with over-corrected designs or molded aspherical elements. These rings arise from uneven distribution and variations in aspherical surfaces, detracting from the smoothness of the blur and making bokeh appear textured or artificial. Coma aberration, another key optical imperfection, distorts off-axis point light sources into asymmetrical, comet-like shapes, which manifests as swirly or elongated bokeh in the corners of the frame. This effect is exacerbated in wide-angle or fast lenses where peripheral rays are not perfectly focused, causing the out-of-focus areas to exhibit rotational rather than uniform circularity, thus compromising the overall aesthetic cohesion of the bokeh. Anti-reflective coatings on elements play a crucial role in mitigating these aberrations' visual impacts by minimizing internal reflections that contribute to and ghosting, which can otherwise introduce harsh edges or veiling in bokeh regions. For instance, multi-layer coatings like those developed by manufacturers such as Nikon and reduce stray light, resulting in smoother transitions and cleaner highlight rendering in out-of-focus areas, particularly under backlit conditions. This enhancement preserves the edge definition of bokeh balls without unwanted artifacts, elevating the perceived quality of the blur. In modern lens designs since the early 2000s, aspherical elements have been increasingly employed to counteract and reduce onion-ring artifacts, as seen in 's Art series lenses like the 105mm f/1.4 DG HSM, which deliver exceptionally smooth and natural bokeh through precise aberration control. These elements allow for compact, high-performance that minimize harshness in out-of-focus rendering while maintaining sharpness in the subject plane. Advancements in the 2020s have extended to apochromatic designs incorporating low-dispersion glasses, such as those in Otus and Art lenses, which further suppress chromatic aberrations to prevent color fringing in bokeh edges, yielding cleaner and more neutral blur characteristics.

Practical Techniques

Camera and Lens Settings

To achieve pronounced bokeh effects in , photographers often prioritize settings to create a shallow (DoF), which isolates the subject by ring the background. Using wide , such as f/1.4 or f/1.8 on compatible , maximizes the size of the blur circles formed by out-of-focus points of light, enhancing the bokeh quality. This approach requires balancing and ISO to maintain proper ; for instance, in low-light conditions, a fast (e.g., 1/125 second) paired with a low ISO (e.g., 100) prevents while keeping minimal. Lens selection plays a crucial role in bokeh production, with prime lenses generally outperforming zoom lenses due to their wider maximum apertures and simpler optical designs that yield smoother out-of-focus rendering. Fast primes like a 50mm f/1.8 or 85mm f/1.4 are favored for portraiture, as they compress the and produce creamy bokeh without the optical compromises often seen in variable-aperture zooms. For extreme bokeh, lenses such as a 100mm f/2.8 are effective, offering close focusing distances that amplify background even at moderate apertures. Camera mode and focus techniques further refine bokeh control. Aperture priority mode (Av or A) allows direct adjustment of the f-stop while the camera automates , simplifying the process for consistent shallow DoF. Manual focus provides precise subject isolation, especially useful for creative effects like isolating specular highlights, though modern mirrorless cameras with advanced systems—such as phase-detection AF with eye-tracking—offer reliable performance for bokeh-heavy shots without manual intervention.

Composition Strategies

Composition strategies for bokeh emphasize the spatial relationships between elements in the to amplify and create visually compelling of the . A fundamental approach is to minimize the between the camera and the while maximizing the separation between the and the ; this compresses the of and exaggerates the out-of-focus rendering, producing smoother and more pronounced bokeh. For instance, in a typical setup, positioning the just a few feet from the with the receding 20-50 feet or more can transform a cluttered scene into one with creamy, abstract . To add dimensionality, photographers employ techniques by arranging multiple elements at distinct distances from the camera, fostering multi-plane bokeh where foreground and background blurs interact to suggest depth. This method involves placing secondary subjects or environmental details in intermediate planes, allowing selective focus on the primary subject while the layered out-of-focus areas form graduated bokeh transitions that guide the viewer's eye. Such compositions are achieved by scouting locations with natural depth variations, like pathways or shelves, ensuring each plane contributes unique textures to the overall bokeh quality without overwhelming the main focus. Lighting setups further enhance bokeh by incorporating discrete point sources in the background, such as strings of holiday lights or distant street lamps, which render as luminous, rounded orbs when blurred. These specular contrast against darker areas, emphasizing the bokeh's and color while avoiding uniform illumination that yields indistinct, muddy ; for optimal results, position lights at least twice the subject-to-camera distance to maintain separation and vibrancy. Uniform backgrounds, like plain walls, should be eschewed in favor of textured or patterned ones to promote varied bokeh forms that add intrigue. In genre-specific applications, bokeh excels in portraits by isolating the against a softened backdrop, reducing distractions and accentuating emotional expressions through compressed background details. For , tight framing of small subjects against distant or layered environments leverages extreme shallow to create enveloping bokeh that highlights intricate textures, often enhanced by subtle point lights for ethereal glow. Urban benefits from composing foreground subjects against expansive cityscapes, where distant signs and vehicle lights form dynamic bokeh clusters; tips include aligning the subject off-center to the with blurred light trails, capturing the metropolis's energy without visual clutter.

Digital Emulation

Software Algorithms

Software algorithms for simulating bokeh primarily rely on computational techniques to approximate the optical effects produced by camera lenses in environments. Basic methods employ kernels, which convolve the image with a rotationally symmetric kernel to create a smooth, circular defocus that mimics simple out-of-focus regions. These kernels are computationally efficient and widely used in editing software for initial approximations, as they distribute intensities evenly around each point, simulating the averaging of rays in the blur circle formation. More advanced depth-aware algorithms enhance realism by incorporating depth estimation to selectively apply based on scene geometry, often using to preserve sharp boundaries and alpha masks to control transparency in blurred areas. For instance, stereo matching or depth networks generate a , which is then used to modulate blur intensity; edges are detected via Sobel operators or Canny algorithms to create masks that prevent halo artifacts around subjects, while alpha channels blend foreground and background layers for seamless transitions. These methods, such as those in depth-of-field synthesis frameworks, allow for variable blur radii proportional to distance from the focal plane, addressing the limitations of uniform Gaussian application. In practical tools, Adobe Lightroom's Lens Blur feature exemplifies depth-aware simulation, leveraging Adobe Sensei AI to generate a depth map from the image and apply customizable bokeh shapes like circles or anamorphic flares, with sliders for blur amount and bokeh boost to refine the effect post-capture. Similarly, neural network-based approaches from the 2020s, such as PyNET, use multi-scale convolutional neural networks (CNNs) trained on paired shallow and deep depth-of-field images to predict realistic bokeh directly, incorporating losses like L1 and structural similarity index (SSIM) for photorealistic results in post-production. Another seminal method, Neural Bokeh, employs a ResNet architecture to learn spatially varying blur kernels from real lens data, enabling the transfer of specific bokeh characteristics (e.g., aperture-induced shapes) to all-in-focus renders via tiled processing for efficiency. Despite these advances, software emulations face inherent limitations, particularly in replicating natural lens aberrations like chromatic shifts or cat-eye distortion, which result in uniformly applied blur that lacks the nuanced, distance-dependent variations of optical bokeh. Artifacts such as edge halos or inconsistent depth estimation in complex scenes with occlusions further highlight the gap between computational approximations and physical optics, often requiring manual refinements for professional use.

Hardware Simulations

Hardware simulations of bokeh in leverage specialized camera systems to generate depth information during capture, enabling post-processing effects that mimic optical shallow without relying solely on lens apertures. Dual-camera setups, introduced prominently in smartphones like the iPhone 7 Plus in 2016, use two closely spaced lenses to capture simultaneous images with shifts, from which disparity-based depth maps are computed to isolate subjects and apply background blur for Portrait mode. These systems measure relative distances in disparity units (1/meters), providing accurate depth data embedded in the photo file for adjustable bokeh simulation, such as foreground sharpening and background defocus. Phase-detection autofocus (PDAF) sensors, integrated into many image sensors since the mid-2010s, further enhance generation by detecting phase differences across split pixels to estimate distances, particularly useful in single-lens configurations for refining bokeh edges. For instance, devices like the 4 employed PDAF alongside dual rear cameras to produce initial depth estimates, which are then used to simulate natural blur patterns. This hardware-assisted approach improves around subjects, reducing artifacts in simulated bokeh compared to purely software-based methods. In the 2020s, advancements like Apple's scanner, debuted in the in 2020, utilize time-of-flight infrared pulses to create high-precision depth maps up to several meters, significantly enhancing low-light performance for Portrait mode bokeh by providing denser point clouds for subject-background separation. Similarly, Google's introduced uDepth, an active for depth sensing on the front camera, enabling more accurate bokeh rendering in selfies and front-facing portraits through hardware-derived disparity data. Light field cameras, such as Lytro's models released from 2012 to 2014 and discontinued in 2017, captured directional light rays via microlens arrays on the , allowing computational refocusing and bokeh by digitally adjusting the focal post-capture. Although influential for proving the concept, Lytro's low resolution limited widespread adoption, but its principles informed subsequent innovations. Some early flagships, such as the and S10, incorporated hardware variable mechanisms, with the S9 introducing the f/1.5–f/2.4 iris in 2018—to control physical during capture, simulating DSLR-like bokeh transitions between wide and narrow apertures for brighter or sharper images. These systems use mechanical blades to adjust light intake and blur intensity in , with depth maps from PDAF aiding precise effect application in portrait shots. Overall, such hardware innovations in flagships like recent Pixels integrate multi-sensor fusion to bridge the gap between mobile and professional , prioritizing accurate depth for realistic bokeh without traditional large lenses.

Broader Applications

In Cinematography

In cinematography, bokeh serves as a dynamic tool to enhance storytelling in motion pictures, where the aesthetic quality of out-of-focus areas evolves with camera movement and scene transitions, building on principles from still photography but adapted for temporal flow. Unlike static images, bokeh in film contributes to emotional depth by isolating subjects amid blurred backgrounds, creating immersion in wide-screen formats common to cinema. This effect is particularly pronounced in narrative films, where it underscores tension, romance, or spectacle, with cinematographers leveraging lens optics to achieve smooth, organic blur that complements the frame's composition. Lens selection plays a pivotal role in crafting cinematic bokeh, with anamorphic lenses favored for their distinctive swirly and oval-shaped out-of-focus rendering, which adds a signature flair. Cooke Optics' Anamorphic/i series, for instance, produces a characteristic oval bokeh through front cylindrical elements combined with rear spherical , delivering the renowned "Cooke Look" of subtle dimensionality and controlled aberrations that has been employed in numerous high-profile productions. These lenses compress the horizontal field while elongating bokeh highlights, evoking a vintage yet polished aesthetic that enhances the epic scale of blockbusters. Key techniques in exploit bokeh for narrative emphasis, such as rack focus pulls that shift the plane of sharpness during a continuous take, revealing or concealing elements while the bokeh transitions fluidly to guide audience attention. This method, executed by focus pullers marking precise distances on the lens barrel, amplifies emotional beats by morphing the background from foreground intrusions to dreamy isolation. choices further influence bokeh's smoothness; standard 24 frames per second paired with a 180-degree shutter angle generates natural that integrates seamlessly with optical bokeh, avoiding the sharpness of higher rates like 60 fps, which can make out-of-focus areas appear unnaturally crisp in fast-paced sequences. Prominent examples from the highlight bokeh's integration into major films, as seen in (2016), where cinematographer used custom anamorphic primes on 35mm film to produce swirling bokeh distortions that romanticized Los Angeles skylines and intimate close-ups, evoking classic musicals while adding modern vibrancy. Post-2020, the shift to cameras has refined bokeh rendering through larger full-frame sensors, as in (2021) and (2024), where Greig Fraser employed rehoused vintage anamorphic lenses on LF and 65 bodies to achieve textured, swirling bokeh in desert vistas and visionary sequences, blending analog character with digital precision for immersive world-building. This evolution allows for consistent bokeh quality across hybrid film-digital workflows, maintaining cinematic allure amid advancing sensor technology.

Artistic and Scientific Uses

In the realm of , bokeh effects are emulated to evoke atmospheric depth and luminosity, transforming ordinary scenes into ethereal compositions. Artists like Philip Barlow have pioneered abstract paintings that replicate the blurred, light-refracted quality of bokeh in urban landscapes, using layered acrylics and oils to simulate out-of-focus as soft, colorful orbs against sharp foreground elements, as seen in his 2020 series exhibited at galleries in the . Light painting, a performative technique, incorporates bokeh by manipulating portable light sources during long exposures to craft custom blur patterns, allowing artists to "draw" glowing, defocused shapes in darkness for conceptual works exploring and motion. This method gained prominence in the through collaborative projects, such as those documented in photography collectives like World Alliance, where LED arrays and shaped diffusers produced intricate bokeh forms symbolizing digital connectivity and abstraction. Artistic installations in the 2010s light festivals further integrated bokeh-inspired designs, with interactive light sculptures generating defocused glows to immerse viewers in blurred, immersive environments. For instance, at the 2015 festival, Olafur Eliasson's "Yellow Spike" installation used programmable LEDs and mist to create dynamic bokeh-like halos, transforming public spaces into galleries of refractive light play, as featured in the event's official archives. Similarly, the 2013 i Light festival showcased "Bokeh" by Kelvin Kong, a suspended array that projected softened light blooms, evoking photographic bokeh in real-time viewer interactions. On the scientific front, bokeh principles underpin innovative optical encoding systems, notably the Bokode developed at in 2009, which embeds imperceptible barcodes within defocused light patterns viewable only through a camera's . This technology leverages bokeh's depth-dependent magnification to enable interaction from distances up to 60 times the tag's diameter, with applications in and augmented interfaces, as detailed in the original paper by Mohan et al. In , bokeh facilitates advanced depth estimation by analyzing defocus cues in images, enhancing models' scene understanding for tasks like segmentation and . Recent 2020s , such as the 2022 method by Wang et al., employs depth networks to render natural bokeh effects, subdividing backgrounds into blur layers based on estimated distances, thereby improving aesthetics and accuracy in applications like autonomous navigation, with reported improvements in perceptual quality metrics over uniform blur baselines. Emerging uses in augmented and (AR/VR) post-2020 harness bokeh rendering for realistic depth-of-field , aligning virtual elements with human visual cues. The 2024 Neural Bokeh framework, presented at IEEE VR, trains diffusion models on lens blur datasets to generate controllable bokeh in real-time VR videography, reducing perceptual artifacts in mixed-reality scenes and enabling applications like immersive with up to 30% better in user studies.