A safelight is a

light source Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terah ...

suitable for use in a photographic

darkroom A darkroom is used to process photographic film, to make prints and to carry out other associated tasks. It is a room that can be made completely dark to allow the processing of the light-sensitive photographic materials, including film and ph ...

. It provides illumination only from parts of the

visible spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called '' visible light'' or simply light. A typical human eye will respond to ...

to which the photographic material in use is nearly, or completely insensitive.

Design

A safelight usually consists of an ordinary light bulb in a housing closed off by a coloured

filter Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...

, but sometimes a special light bulb or fluorescent tube with suitable filter material or phosphor (in fluorescent tubes) coated directly on the glass is used in an ordinary fixture. Differently sensitised materials require different safelights. In traditional

black-and-white Black-and-white (B&W or B/W) images combine black and white in a continuous spectrum, producing a range of shades of grey. Media The history of various visual media began with black and white, and as technology improved, altered to color. ...

photographic printing,

photographic paper Photographic paper is a paper coated with a light-sensitive chemical formula, like photographic film, used for making photographic prints. When photographic paper is exposed to light, it captures a latent image that is then developed to form a ...

s normally are handled under an amber or red safelight, as such papers typically are sensitive only to blue and green light.

Orthochromatic In chemistry, orthochromasia is the property of a staining, dye or stain to not change color on binding to a target, as opposed to Metachromasia, metachromatic stains, which change color. The word is derived from the Greek ''wikt:ortho-, orthos'' ...

papers and films are also sensitive to yellow light and must be used only with a deep red safelight, not with an amber one.

Panchromatic Panchromatic emulsion is a type of black-and-white photographic emulsion that is sensitive to all wavelengths of visible light. Description A panchromatic emulsion renders a realistic reproduction of a scene as it appears to the human eye, altho ...

films and papers, nominally sensitive to the entire spectrum, sometimes have a region of minimum in their range of sensitivity that allows the careful use of safelight confined to that part of the spectrum. For example,

Kodak The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpor ...

Panalure Photographic paper is a paper coated with a light-sensitive chemical formula, like photographic film, used for making photographic prints. When photographic paper is exposed to light, it captures a latent image that is then developed to form a v ...

panchromatic paper is tolerant of limited exposure to light filtered through a Kodak 13 Safelight Filter. Other panchromatic materials must be handled only in total darkness. Many photosensitive materials used in technical and industrial applications, such as

photoresist A photoresist (also known simply as a resist) is a light-sensitive material used in several processes, such as photolithography and photoengraving, to form a patterned coating on a surface. This process is crucial in the electronic industry. ...

, are sensitive only to blue, violet, and ultraviolet light and may be handled under a brighter yellow safelight. Low-pressure sodium vapour lamps sometimes are used in larger industrial darkrooms. They emit nearly monochromatic light at 589 nm (yellow), to which the materials are insensitive; as a result they can be extremely bright while still "safe". The word "safe" in "safelight" is relative, as in most cases, a sensitised material eventually will be affected by its safelight if exposed to it for an extended length of time.

References

Photography equipment Types of lamp {{photography-stub

Design

See also

References