Diffuser (optics)

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In optics, 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. Diffused light can be easily obtained by reflecting light from a white surface, while more compact diffusers may use translucent material, including ground glass, teflon, opal glass, and greyed glass.

Contents

Types

Perfect reflecting diffuser

A perfect (reflecting) diffuser (PRD) is a theoretical perfectly white surface with Lambertian reflectance (its brightness appears the same from any angle of view). It does not absorb light, giving back 100% of the light it receives. [1] Reflective diffusers can be easily characterised by scatterometers. [2]

Diffractive diffuser/homogenizer

A diffractive diffuser is a kind of diffractive optical element (DOE) that exploits the principles of diffraction and refraction. It uses diffraction to manipulate 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. [3] [2]

Applications

Effects of a diffuser in close-up photography (for more information, see file description) Laubfrosch Diffusor.jpg
Effects of a diffuser in close-up photography (for more information, see file description)

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 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. 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, which is another type of lighting gel. Shōji 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 photographers, since harsh light and hard shadows are usually not considered flattering in a portrait.

Objective-lens filters

Top left: original image. Bottom left: diffusion filter. Top right: cross-screen effect. Bottom right: lomo effect. Verbluhende Sauerkirsche.jpg
Top left: original image. Bottom left: diffusion filter. Top right: cross-screen effect. Bottom right: lomo effect.

"Diffusion filter" may also refer to a translucent photographic filter used for a special effect. When used in front of the camera lens, a diffusion filter softens subjects and generates a dreamy haze. This effect can also be improvised by smearing petroleum jelly 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 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 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.

See also

Related Research Articles

The film industry is built upon many technologies and techniques, drawing upon photography, stagecraft, music, and many other disciplines. Following is an index of specific terminology applicable thereto.

<span class="mw-page-title-main">Red-eye effect</span> Photography appearance

The red-eye effect in photography is the common appearance of red pupils in color photographs of the eyes of humans and several other animals. It occurs when using a photographic flash that is very close to the camera lens in ambient low light.

<span class="mw-page-title-main">Interference filter</span>

An interference filter, dichroic filter, or thin-film filter is an optical filter that reflects some wavelengths (colors) of light and transmits others, with almost no absorption for all wavelengths of interest. An interference filter may be high-pass, low-pass, bandpass, or band-rejection. They are used in scientific applications, as well as in architectural and theatrical lighting.

<span class="mw-page-title-main">Light meter</span> Device used to measure the amount of light

A light meter is a device used to measure the amount of light. In photography, an exposure meter is a light meter coupled to either a digital or analog calculator which displays the correct shutter speed and f-number for optimum exposure, given a certain lighting situation and film speed. Similarly, exposure meters are also used in the fields of cinematography and scenic design, in order to determine the optimum light level for a scene.

<span class="mw-page-title-main">Flash (photography)</span> Device producing a burst of artificial light

A flash is a device used in photography that produces a brief burst of light at a color temperature of about 5500 Kelvin to help illuminate a scene. A major purpose of a flash is to illuminate a dark scene. Other uses are capturing quickly moving objects or changing the quality of light. Flash refers either to the flash of light itself or to the electronic flash unit discharging the light. Most current flash units are electronic, having evolved from single-use flashbulbs and flammable powders. Modern cameras often activate flash units automatically.

<span class="mw-page-title-main">Color gel</span> Material used to color light or correct color

A color gel or color filter, also known as lighting gel or simply gel, is a transparent colored material that is used in theater, event production, photography, videography and cinematography to color light and for color correction. Modern gels are thin sheets of polycarbonate, polyester or other heat-resistant plastics, placed in front of a lighting fixture in the path of the beam.

Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.

<span class="mw-page-title-main">Photographic filter</span> Camera accessory consisting of an optical 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 glass or plastic disk in a metal or plastic ring frame, which can be screwed into the front of or clipped onto the camera lens.

<span class="mw-page-title-main">Guide number</span>

When setting photoflash exposures, the guide number (GN) of photoflash devices is a measure photographers can use to calculate either the required f‑stop for any given flash-to-subject distance, or the required distance for any given f‑stop. To solve for either of these two variables, one merely divides a device's guide number by the other.

<span class="mw-page-title-main">Key light</span> First light in a photographic or filmmaking lighting scheme

The key light is the first and usually most important light that a photographer, cinematographer, lighting cameraman, or other scene composer will use in a lighting setup. The purpose of the key light is to highlight the form and dimension of the subject. The key light is not a rigid requirement; omitting the key light can result in a silhouette effect. Many key lights may be placed in a scene to illuminate a moving subject at opportune moments.

<span class="mw-page-title-main">Fill light</span> Lighting used to reduce the contrast of a scene

In television, film, stage, or photographic lighting, a fill light may be used to reduce the contrast of a scene to match the dynamic range of the recording media and record the same amount of detail typically seen by eye in average lighting and considered normal. From that baseline of normality, using more or less fill will make shadows seem lighter or darker than normal, which will cause the viewer to react differently, by inferring both environmental and mood clues from the tone of the shadows.

<span class="mw-page-title-main">Hard and soft light</span> Types of lighting in photography and filmmaking

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 produces harsher shadows.

<span class="mw-page-title-main">Optical tomography</span>

Optical tomography is a form of computed tomography that creates a digital volumetric model of an object by reconstructing images made from light transmitted and scattered through an object. Optical tomography is used mostly in medical imaging research. Optical tomography in industry is used as a sensor of thickness and internal structure of semiconductors.

<span class="mw-page-title-main">Portrait photography</span> Type of photography aimed at expressing the personality of the human subject(s)

Portrait photography, or portraiture, is a type of photography aimed toward capturing the personality of a person or group of people by using effective lighting, backdrops, and poses. A portrait photograph may be artistic or clinical. Frequently, portraits are commissioned for special occasions, such as weddings, school events, or commercial purposes. Portraits can serve many purposes, ranging from usage on a personal web site to display in the lobby of a business.

The following outline is provided as an overview of and topical guide to photography:

<span class="mw-page-title-main">Lightbox</span> Translucent surface illuminated from behind

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.

<span class="mw-page-title-main">Ring flash</span> Camera flash equipment

A ring flash is a circular light that is often operated with a camera lens in the center to take photographs. Unlike point light sources, a ring flash can illuminate a subject with minimal shadows by closely and evenly surrounding the optical axis of the camera lens. This makes it a popular choice for various types of photography, including macro, portrait and fashion photography.

<span class="mw-page-title-main">Reflector (photography)</span> Reflective surface used to redirect light towards a given subject or scene, used in photography

In photography and cinematography, a reflector is an improvised or specialised reflective surface used to redirect light towards a given subject or scene.

<span class="mw-page-title-main">Beauty dish</span> Photographic lighting device

A beauty dish is a photographic lighting device that uses a parabolic reflector to distribute light towards a focal point. The light created is between that of a direct flash and a softbox, giving the image a wrapped, contrasted look, which adds a more dramatic effect.

Articles related to the field of motion pictures include:

References

  1. Fairchild, Mark D. (8 July 2005). Color Appearance Models. John Wiley & Sons. p. 65. ISBN   0-470-01216-1.
  2. 1 2 "Page Title". www.zebraoptical.com.
  3. Walecki, Wojciech, and Peter Walecki. "Robust diffuser and roughness metrology tool for LED manufacturing." SPIE OPTO. International Society for Optics and Photonics, 2015.