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

, 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 Hard and soft light are different types of lighting that are commonly used in photography and filmmaking. Soft light is light that tends to "wrap" around objects, projecting diffused shadows with soft edges, whereas hard light is more focused and ...

. 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 scattering of light. On a macroscopic scale (one in which the dimensions ...

material, including ground glass,

teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Che ...

, 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 technically, the su ...

(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 (DOE) that exploits the principles of

diffraction Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a s ...

and

refraction In physics, refraction is the redirection of a wave as it passes from one 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 commonly observed phenomen ...

. It uses diffraction to manipulate

monochromatic light {{Short description, Electromagnetic radiation with a single constant frequency In physics, monochromatic radiation is electromagnetic radiation with a single constant frequency. When that frequency is part of the visible spectrum (or near it) the ...

, 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 Flash, flashes, or FLASH may refer to: Arts, entertainment, and media Fictional aliases * Flash (DC Comics character), several DC Comics superheroes with super speed: ** Flash (Barry Allen) ** Flash (Jay Garrick) ** Wally West, the first Kid F ...

of a

camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...

. 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 Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associa ...

, which is another type of lighting gel.

Shōji A is a door, window or room divider used in traditional Japanese architecture, consisting of translucent (or transparent) sheets on a lattice frame. Where light transmission is not needed, the similar but opaque ''fusuma'' is used (oshiire/ ...

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 and its expressions are predominant. The intent is to display the likeness, personality, and even the mood of the person. For this re ...

photographers, 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 A lightbox is a translucent surface illuminated from behind, used for situations where a shape laid upon the surface needs to be seen with high contrast. Types Several varieties exist, depending on their purpose: * Various backlit viewing d ...

, 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 are traditional Japanese confections that are often served with green tea, especially the types made of ''mochi'', ''anko'' (azuki bean paste), and fruit. ''Wagashi'' are typically made from plant-based ingredients. History In Japan, the wor ...

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 SFX, 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 imagined events in a story or virtual w ...

. When used in front of the

camera lens A camera lens (also known as photographic lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capab ...

, 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 ...

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 classificatio ...

. 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 its ...

on a

UV filter UV filters are compounds, mixtures, or materials that block or absorb ultraviolet (UV) light. One of the major applications of UV filters is their use as sunscreens to protect skin from sunburn and other sun/UV related damage. After the inventi ...

or shooting through a nylon stocking. Diffusion filters may be uniform or may have a clear center area to create a vignette 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 refers to the optical phenomena displayed by the mineraloid gemstone opalopalescent. 2019. In Noah Webster's 1828 American Dictionary of the English Language. Retrieved January 7, 2019, from https://1828.mshaffer.com/d/word/opalesc ...

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