optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...

, a diffuser (also called a light diffuser or optical diffuser) is any material that diffuses or scatters light in some manner to transmit

soft light Soft may refer to: * Softness, or hardness, a property of physical materials Arts and entertainment * ''Soft!'', a novel by Rupert Thomson, 1988 * Soft (band), an American music group * ''Soft'' (album), by Dan Bodan, 2014 * ''Softs'' (album), ...

. Diffused light can be easily obtained by reflecting light from a white surface, while more compact diffusers may use

translucent In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable light scattering by particles, scattering of light. On a macroscopic scale ...

material, including

ground glass Ground glass is glass whose surface has been ground to produce a flat but rough ( matte) finish, in which the glass is in small sharp fragments. Ground glass surfaces have many applications, ranging from ornamentation on windows and table glass ...

teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from ...

, opal glass, and greyed glass.

Types

Perfect reflecting diffuser

A perfect (reflecting) diffuser (PRD) is a theoretical perfectly white surface with

Lambertian reflectance Lambertian reflectance is the property that defines an ideal "matte" or diffusely reflecting surface. The apparent brightness of a Lambertian surface to an observer is the same regardless of the observer's angle of view. More precisely, the ref ...

(its brightness appears the same from any angle of view). It does not absorb light, giving back 100% of the light it receives. Reflective diffusers can be easily characterised by scatterometers.{{cite web, url=http://www.zebraoptical.com/roughnessviascatterometry.html, title=Page Title, website=www.zebraoptical.com

Diffractive diffuser/homogenizer

A diffractive diffuser is a kind of

diffractive optical element Diffraction is the deviation of waves from straight-line propagation without any change in their energy due to an obstacle or through an aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wav ...

(DOE) that exploits the principles of

diffraction Diffraction is the deviation of waves from straight-line propagation without any change in their energy due to an obstacle or through an aperture. The diffracting object or aperture effectively becomes a secondary source of the Wave propagation ...

and

refraction In physics, refraction is the redirection of a wave as it passes from one transmission medium, medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commo ...

. It uses diffraction to manipulate

monochromatic light {{More citations needed, date=May 2023 In physics, monochromatic radiation is electromagnetic radiation with a single constant frequency or wavelength. When that frequency is part of the visible spectrum (or near it) the term monochromatic light ...

, giving it a specific spatial configuration and intensity profile. Diffractive diffusers are commonly used in commercially available LED illumination systems. Usually, the diffuser material is GaN or fused silica with processed rough surfaces. LED diffusers can be characterized online using scatterometry-based metrology.Walecki, Wojciech, and Peter Walecki. "Robust diffuser and roughness metrology tool for LED manufacturing." SPIE OPTO. International Society for Optics and Photonics, 2015.

Applications

Diffusion filters may be used to diffuse the light falling on the subject, or placed between the camera and the subject for a hazy effect.

Lighting diffusers, transmitting and reflecting

A flash diffuser (also called a speedlight diffuser, or shoot-through diffuser) spreads the light from the flash of a

camera A camera is an instrument used to capture and store images and videos, either digitally via an electronic image sensor, or chemically via a light-sensitive material such as photographic film. As a pivotal technology in the fields of photograp ...

. A diffusion filter of this type may also be used in front of a non-flash studio light to soften the light on the scene being shot; such filters are used in still photography, in film lighting, and in

stage lighting Stage lighting is the craft of lighting as it applies to the production of theater, dance, opera, and other performance arts.

. In the film and stage industry, a diffusion filter may also be called diffusion gel, or just diffusion. This is by analogy to a

color gel A color gel or color filter ( Commonwealth spelling: colour gel or colour filter), also known as lighting gel or simply gel, is a transparent colored material that is used in theater, event production, photography, videography and cinematogr ...

, which is another type of

lighting gel A color gel or color filter ( Commonwealth spelling: colour gel or colour filter), also known as lighting gel or simply gel, is a transparent colored material that is used in theater, event production, photography, videography and cinematogra ...

Shōji A is a door, window or room divider used in traditional Japanese architecture, consisting of Transparency and translucency, translucent (or transparent) sheets on a lattice frame. Where light transmission is not needed, the similar but opaq ...

are diffusing window/doors. Reflecting diffusers for photography are generally called " reflectors". In effect, the light will not come from one concentrated source (like a spotlight), but rather will spread out, bounce from reflective ceilings and walls, thus getting rid of harsh light, and hard shadows. This is particularly useful for

portrait A portrait is a painting, photograph, sculpture, or other artistic representation of a person, in which the face is always predominant. In arts, a portrait may be represented as half body and even full body. If the subject in full body better r ...

photographers A photographer (the Greek φῶς (''phos''), meaning "light", and γραφή (''graphê''), meaning "drawing, writing", together meaning "drawing with light") is a person who uses a camera to make photographs. Duties and types of photograp ...

, since harsh light and hard shadows are usually not considered flattering in a portrait. File:Blitz Diffusor (fcm).jpg, Diffuser on a camera flash. Made from a sheet of paper, a rubber band, and two staples. File:Silver bounce (4097154692).jpg, A more formal diffuser filter over a camera flash, flanked by reflectors File:Tools of the trade (6484757517).jpg, Flash diffuser to be mounted on a camera File:Elinchrom flash equipment DSCF2813.JPG, Softbox diffuser; a larger area spreads the light more File:Foreign Secretary's Ramadan message (4852950309).jpg, A lighting technician holds a reflector to diffuse the light falling on a politician File:DIY Lightbox.jpg, A home-made lightbox, designed to produce images with diffuse lighting from all angles File:WikiDACH 2019, Nürnberg (P1080060).jpg, Lightbox photography File:Wagashi Lighting for Japanese TV Program Recording.jpg, Both transmitting (softbox) and reflecting diffusors are used to light

wagashi is traditional Japanese confectionery, typically made using plant-based ingredients and with an emphasis on seasonality. ''Wagashi'' generally makes use of cooking methods that pre-date Western influence in Japan. It is often served with green ...

for a television program File:Studioleuchte 2012-04 by-RaBoe-05.jpg, Studio lights, one white, two metallized File:FSboomerang.JPG, Theatrical colour magazine or boomerang. Placed in front of a stage light, it gives quick changes in lighting gel, including a diffusion filter File:障子に映る影Img568.jpg,

Objective-lens filters

"Diffusion filter" may also refer to a

photographic filter In photography and cinematography, a filter is a camera accessory consisting of an optical filter that can be inserted into the optical path. The filter can be of a square or oblong shape and mounted in a holder accessory, or, more commonly, a ...

used for a

special effect Special effects (often abbreviated as F/X or simply FX) are illusions or visual tricks used in the theatre, film, television, video game, amusement park and simulator industries to simulate the fictional events in a story or virtual world. ...

. When used in front of the

camera lens A camera lens, photographic lens or photographic objective is an optical lens (optics), lens or assembly of lenses (compound lens) used in conjunction with a camera body and mechanism to Imaging, make images of objects either on photographic film ...

, a

diffusion Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...

filter softens subjects and generates a dreamy

haze Haze is traditionally an atmospheric phenomenon in which dust, smoke, and other dry particulates suspended in air obscure visibility and the clarity of the sky. The World Meteorological Organization manual of codes includes a classificati ...

. This effect can also be improvised by smearing

petroleum jelly Petroleum jelly, petrolatum (), white petrolatum, soft paraffin, or multi-hydrocarbon, CAS number 8009-03-8, is a semi-solid mixture of hydrocarbons (with carbon numbers mainly higher than 25), originally promoted as a topical ointment for i ...

on a UV filter or shooting through a nylon stocking. Diffusion filters may be uniform or may have a clear center area to create a

vignette Vignette may refer to: * Vignette (entertainment), a sketch in a sketch comedy * Vignette (graphic design), decorative designs in books (originally in the form of leaves and vines) to separate sections or chapters * Vignette (literature), short, i ...

of diffused area around the clear center subject.

Diffuser materials

Silk sheets can also be used as diffusers, and in fact were until the invention of translucent plastics. "Opal" is a common translucent or

opalescent Opalescence or play of color is an optical phenomena, optical phenomenon associated with the mineraloid gemstone opal,opalescent. 2019. In Noah Webster's 1828 American Dictionary of the English Language. Retrieved January 7, 2019, from https:// ...

diffusion. Recently, photopolymers have been used for making holographic diffusers. Photopolymers offer better performance than other materials and have a large viewing angle. Also, the process of synthesizing photopolymers is much simpler.

References

Optical components Photography equipment Optical filters Photographic lighting Stage lighting