Glossary of Technical Terms

There are a lot of technical terms and jargon associated with photography which can be confusing. Hopefully, this glossary can help with some explanations. It is not a full list, for that, a photographic dictionary is required. But here are some widely used terms, in alphabetical order.

A | B | C | D | E | F | G | H | I | L | M | N | P | R | S | T | U | V | W | X,Y,Z



The opening in a lens which allows light through. The size of the opening can usually be controlled and is measured in f-stops.

Aperture Priority

A semi automatic exposure setting, allowing the photographer to choose the aperture setting of the camera lens, while the metering system of the camera automatically selects the correct shutter speed for prevailing light conditions. See Exposure.


American Standards Association. Film speed rating, expressed as a number. The higher the number, the faster or more sensitive the film to light. More recently known as ISO.


The facility of some lenses to focus on the subject without manual adjustment.



Light coming from behind the subject. Extra lighting may be needed to light the front of the subject if a silhouette effect is to be avoided.


An umbrella shaped attachment used in studio lighting to reflect light onto the subject.


The most common bromide used in photography is silver bromide, which is sensitive to light and is widely used in the manufacture of films and papers. See Emulsion, Silver halides.

Burning in

To give increased exposure to one area of a print when hand printing.

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Cable release

A flexible mechanism attached to the shutter release of the camera so that the picture may be taken from a distance and / or without moving the camera.


A light proof body with a shutter mechanism and a lens that allows light to enter, in order to record the action of light on a photosensitive material. Some types of camera are:


The difference between light and dark areas of a photographic image. The extent of the variation is known as the tonal range. A contrasty image is one where there is a great degree of light and dark areas and not so many mid tones.

Contact sheet

A print that shows positive images made from all the negatives on one film at the actual size of the negative. Usually made to aid selection of the best images from a film before enlargement.

Converging parallels

An effect where vertical lines in a photographic image that should be parallel look as if they are meeting. Typically caused by tipping the camera upwards when taking a picture of a tall building.

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A direct positive process where the image was created by the action of light on copper plate coated with polished silver and developed in mercury vapour, invented by Louis Daguerre in 1839.


A light proof room where photographic processing takes place.

Depth of field

The amount of a photographic image that is in focus in relation to the distance from the camera. Depth of field is affected by the aperture and focal length of the lens, and the distance of the subject from the camera.


A solution that reduces silver halides in the photographic emulsion that have been exposed to light to metallic silver in order to create a visible image.


To give decreased exposure to one area of a print when hand printing.



Photographic emulsion is a combination of light sensitive crystals that are coated onto acetate to make film or paper to make prints. The crystals usually consist of silver halides, which are compounds of silver iodide, bromide and chloride.


A photographic print that is larger than the negative size.


A device used in the darkroom to make an enlargement, where light is projected through a negative and a lens to create an image on a piece of photographic paper or other light sensitive material.


The act of allowing light to react with a photosensitive material when taking a photo or when making an enlargement. The intensity of the light source and the duration of time the material is exposed for is measured in order to produce the correct exposure. Most cameras have a built in exposure meter that does this.

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Cellulose acetate coated with silver halide emulsion to create a light sensitive material that can be passed through a camera. There are many different types and sizes of film available for different purposes.

Film speed

A number which denotes how sensitive the film is to light. The higher the number the more sensitive, or fast, the film is said to be. Fast film contains more and bigger crystals of silver halide which increases sensitivity. See ASA / ISO.


A translucent cover over a lens that changes the nature of the light to create special effects, to reduce exposure, or to remove parts of the light spectrum.


A processing solution used to make a photographic image permanent by dissolving unexposed silver halides out of a photographic emulsion.


A burst of artificial light used to add light to a photographic situation. A flashgun can be built into a camera, or a separate unit connected via the hot shoe.


A number on a lens that denotes the size of the aperture. The number is obtained by dividing the focal length of the lens with the diameter of the aperture. The smaller the number, the wider the aperture. See Depth of field.

Focal length

The distance from the lens to the film plane of a camera. The focal length determines the size and perspective of the image produced. A wide angle lens has a short focal length, a telephoto lens has a long focal length.


The sharpness of the photographic image.

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The size of the particles of silver in a photographic image. If these are fairly large and noticeable the image is said to be grainy. This can be the case if a fast film is used, if the lighting is insufficient, or if a very big enlargement is made from a small negative. Fine grained images are produced if lighting is good, slow film is used, and enlargement size is not too great in relation to the negative size.


High key

Description of a photographic image which has predominantly light tones and little contrast.

Hot shoe

The contact on a camera for fixing a flashgun so that it fires when the shutter is released.


Another term for fixer.


Incident light

Light falling directly on a subject; exposure for incident light is often measured in the lighting studio using a light meter with a wide angle of acceptance.


International Standardisation Organisation. Film speed rating, expressed as a number. The higher the number, the faster or more sensitive the film to light. See ASA / Film speed.

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Latent image

The invisible image present in exposed but undeveloped film or paper. Development converts the latent image to a visible image. See Developer.


A system of curved glass surfaces used to form an image by focusing rays of light. Some types of lenses are:

Light meter

Or exposure meter, a device built in to the camera, or used separately in the lighting studio to determine exposure by measuring the action of light on a photoelectric cell. The meter can be used to measure incident or reflected light.

Low key

Description of a photographic image which has predominantly dark tones and little contrast.


Mid tones

The tones in between the lightest and darkest areas of a photographic image. A predominance of mid tones creates a low contrast image. See Contrast.


Black and white, or one other colour and white in a photographic image.


A composite image made from different source images and materials combined or juxtaposed.

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In black and white the tones are in reverse to those of the original subject, in colour negatives the original tones are reproduced as their complementary colours. Producing a photographic negative is often the first stage in the making of a positive print, and is a unique article from which many prints can be made.



A black and white film or photographic emulsion that is sensitive to all colours of the spectrum except red and orange. Used for special reprographic processes.


To give more than normal development to a film or print. See Push processing.


Happens when too much light reaches the photographic emulsion, may be caused by accident or design in order to control density and contrast of an image. Overexposure causes too much silver to be deposited on the film, producing a dense negative that is difficult to print from.



A black and white film or photographic emulsion that is sensitive to all colours of the spectrum especially blue. Most black and white films in use are of this type.


Photographic paper is made by coating light sensitive emulsion onto paper so that prints can be produced. Black and white papers can be handled under red or yellow safelighting, colour papers must be handled in total darkness. There are many varieties and surface effects available. Some types of papers are:


An image made without a camera, by placing objects onto photographic paper under an enlarger or light source, then processing the result.

Pinhole camera

A simple camera with a small hole instead of a lens, sometimes made with a pin. Can be easily constructed from shoe boxes or biscuit tins, and with experimentation can produce images of surprisingly high optical quality.

Push processing

A way of processing film by extending developing time so that the film operates at maximum sensitivity. Useful for obtaining images from low light situations. See Uprating.

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Red eye

Direct flash reflecting off the blood vessels of the retina at the back of the eye causes this unattractive effect in colour photography.

Reflected light

Light reflected by the subject into the lens of the camera.



A red, orange or yellow light used in the darkroom for black and white photographic printing.


The mechanism in a camera which opens to let in light. Shutter speed can be controlled so that the slower it is the more light reaches the film. When long shutter speeds are used, a tripod may be necessary to hold the camera still.

Shutter speed priority

A semi automatic exposure setting, allowing the photographer to choose the shutter speed setting of the camera, while the metering system of the camera automatically selects the correct aperture for prevailing light conditions. See Exposure.

Silver halides

Light sensitive crystals consisting of silver iodide, bromide and chloride used to produce photographic emulsion.


A tubular or conical attachment placed over a studio light which concentrates light into a narrow beam in order to place a highlight on a small area of the subject.

Soft box

A large canvas box shaped attachment placed over a studio light to diffuse light and create a large area of shadowless light on the subject.


Unwanted spreading of light from the edges of a light source.

Spill kill

Attachments for studio lights to prevent unwanted spreading of light.


A processing solution of acetic acid which stops development of film and papers instantly, and prevents contamination of other processing chemistry. Also means a doubling or halving of exposure by changing aperture, shutter speed or film speed rating by one setting while photographing, or by changing the aperture of the enlarger by one setting while making a print.

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Test strip

Strip cut from a sheet of photographic paper used to test several different exposure levels before deciding the correct exposure when making a print.

Tonal range

Light, dark and mid tones in a photographic image are described in terms of its tonal range. If there are all tones present it is said to have a full tonal range, if there is a predominance of either light or dark tones, the tonal range is said to be restricted.


Process using solutions of iron, sulphur, selenium or other chemistry to change the colour of a black and white print and / or increase its archival permanence.


A three legged device used to support the camera and keep it still in windy conditions and / or when using slow shutter speeds and / or long and heavy lenses.



To give less than normal development to a film or print, which means the conversion of silver halides to metallic silver will be incomplete so making the image less dense.


Happens when insufficient light reaches the photographic emulsion, may be caused by accident or design in order to control density and contrast of an image. Underexposure causes too little silver to be deposited on the film, creating thin negatives which are difficult to print from.


This is done by changing the film snpeed setting on the camera to a higher ASA / ISO setting than the film actually is. This can be done in reduced light conditions when it is not practical to use flash. The film will be in effect underexposed, this is normally compensated for by push processing.

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A photographic image which fades off to the edges, a technique popular in Victorian portrait photography.


Wetting agent

A detergent like substance that prevents a surface from repelling liquids, so aiding the washing process of photographic films and papers.

X, Y, Z


Black and white film using colour technology; combines high speed sensitivity with a fine grain structure. Because the film contains a dye combined with silver halides in the emulsion it can go through a processing machine using the same C41 chemistry as ordinary colour film, so XP2 is quick, convenient and inexpensive to have processed commercially.

Zone system

A complicated system of tonal control in black and white photography pioneered by Ansel Adams.

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