JPEG (Joint Photographic Experts Group) A file format used widely for digital images. A variable amount of compression can be used to vary both the detail stored and the resulting size of the file. It is the standard format used by most digital cameras (although RAW or TIFF formats may be available for the highest resolution capture settings). 


Kelvin (K) Unit of measurement used to describe the color temperature of light sources. See Color temperature.

Key light Alternative term for Main light


Large-format camera See View camera

Lasso Selection tool used in digital manipulation software. Allows you to outline an area of an image by drawing a series of points around it.

Latent image Invisible image on film or photographic printing paper formed by the action of light from the subject and made visible by the development process.

Layer Feature available on some digital manipulation software that allows you to lay different versions or elements of an image on top of each other. The original image can be protected as the background layer, whilst alterations are made to copy layers. Layers can be opaque – or they can be merged with layers below in a number of different ways. Layers are an essential way of working for any serious manipulation work.

LCD (liquid crystal display) Type of display panel used widely on cameras to provide information to the user. Color LCDs are capable of showing detailed images, and are often used as viewing screens on digital cameras.

LED (light emitting diode) Colored indicator lamp used on many cameras for a variety of purposes.

Lens Glass or plastic optical instrument that can refract light. A photographic lens consists of different-shaped glass elements arranged in groups to form a compound lens. In a compound lens, some elements are convex in shape, causing rays of light to converge, and some concave, causing rays to diverge.

Lens hood Attachment made of metal or rubber that screws into the filter mount on the front of a lens and prevents unwanted light from reaching the surface of the lens and affecting the image.

Lens speed Refers to the maximum aperture available with a lens. Lenses with wide maximum apertures admit most light, and so can be used in dimmer lighting conditions or to compensate for faster shutter speeds; these are known as fast lenses.

Light box Box containing fluorescent tubes with an opaque glass or plastic top used for viewing transparencies.

Light meter See Exposure meter. Linear perspective Sense of depth and

distance in a two-dimensional photograph caused by the apparent convergence of parallel lines receding from the camera.

Lith film Black-and-white film with a tonal range that is reduced to black and white with only minimal greys. Must be developed with a special lith developer.

Low-key image An image composed predominantly of dark tones or colors. 


Macro Term used to describe equipment or features that allow you to take pictures at a closer shooting distance than usual, to provide a more magnified image.

Magic wand Selection tool used in digital manipulation that lets you select an area of similar color or tone simply by clicking on it.

Main light Principal lighting unit that provides illumination for a subject or scene.

Marquee Selection tool used in digital image manipulation programs that allows you to draw regular shapes – such as ovals or rectangles.

Medium-format camera Camera with a picture format larger than 35mm but smaller than a view camera. The rolls of film measure 6cm (2 1⁄4 in) across - but the image size varies from camera to camera. Popular formats include 6 x 6cm, 6 x 4.5cm and 6 x 7cm – with a variety of panoramic sizes also available.

Megabyte (MB) Unit for measuring the capacity of computer memory. Equal to 1,024 bytes (two to the power of ten bytes).

Megapixel Measurement of the resolution of a digital camera, equal to one million pixels.

Memory card A removable electronic card used in most digital cameras to save and store digital images. Cards of different memory capacity are available.

Mirror lens Telephoto lens with mirrors replacing some of the glass elements found in a traditional lens. The effect of the mirrors is to reflect light rays up and down the length of the lens to produce a long focal length in a relatively short lens barrel. The aperture of such lenses is usually fixed at around f8. Also known as a catadioptric or reflex lens.

Modeling lamp Low-wattage, continuous- output lamp mounted in the lighting head of a flash unit. Allows the photographer to preview the effects of light and shade, especially the fall of the shadows that will be produced when the flash fires.

Monochromatic Describes a photographic image that is solely or predominantly composed of a single color or shades of a single color.

Montage Composite picture made from a number of photographs.

Motordrive Automatic film advance system, either built into the camera or available as an add-on accessory. The system allows continuous shooting, taking picture after picture as long as the trigger is held down. 

Motorized film transport Automatic feature found on many cameras, which uses a motor inside the camera to advance the film at the beginning of a roll, advance the film after each exposure, and rewind the film after the last shot is taken.

Multiple exposure Technique of making more than one exposure appear on the same image. Sometimes done for special effect but can also occur due to a fault with the film advance system. 


Negative Developed film image in which colors or tones of the original subject are reversed. An intermediate stage in the production of a print.

Neutral density filter Gray-colored lens filter that reduces the amount of light reaching the film without affecting color balance. 


Off the film (OTF) A light-reading system that gauges exposure by measuring the amount of light being reflected by the film.

Open flash Button on some flashguns that allows the flash to be fired without exposing the film. Very important feature on any flash unit if exposure using a flash meter is required. Also used for “painting with light” technique.

Opening up Increasing the size of the aperture to allow more light to reach the film.

Overexposure Occurs if a film receives too much light, either by exposing it to too bright a light or by allowing the light to act on it for too long. It results in light prints or slides and a reduction in subject contrast. 


Pan-and-tilt head Versatile type of camera- mounting system found on some tripods. The tripod head can be swiveled from side to side or tilted up and down, and the camera turned either horizontally or vertically and locked securely in any position. See also Tripod.

Panning Action of turning the camera while the shutter is open to keep pace with a moving subject. The subject should appear reasonably sharp while all stationary parts of the scene are blurred. 

Panorama A broad, continuous scene taken either with a panoramic camera or produced by taking a series of different photographs of a scene and joining the individual pictures together to create a panoramic view.

Panoramic camera Camera that offers an image size where the width is significantly greater than the height.

Parallax error Framing error almost always associated with direct vision viewfinders, which results in a slight difference in viewpoint between the image as seen in the viewfinder and that recorded on the film.

Passive autofocus Autofocus system that adjusts the focus of the lens by looking at the image itself, rather than actively measuring
the subject distance. This type of autofocus
is widely used on 35mm SLRs and on some other types of camera. It is also known as contrast-detection or phase-detection autofocus.

Pentaprism Five-sided prism usually found on the top of SLR cameras. Its inside surfaces are silvered so that the image produced by the reflex mirror appears in the viewfinder the right way up and correctly oriented left to right.

Perspective control lens See Shift lens. Photoflood See Floodlight.

Photogram Picture made by placing opaque and/or translucent objects in contact with photographic paper or film, exposing the paper to light, and then developing normally.

Photomicrography Production of larger- than-life images of small subjects by attaching the camera to a microscope.

Pixel Short for picture element. A single light- sensitive cell in a digital camera's image sensor. The basic unit used when measuring the maximum resolution of a digital camera or a digital image.

Pixelated A digital image in which the individual picture elements that make it up have become visible. This is usually due to over-enlargement to poor resolution of the original image. The effect can also be created with manipulation software, using effects such as a mosaic filter.

Plug-in Piece of software which adds functionality to an existing computer program. Plug-ins are available for some digital image manipulation programs, providing an increased range of effects and transformations.

Point-and-shoot See Compact

Polarizer A filter that only lets through light vibrating in one plane. It can be used to deepen the color of part of a picture, such as the sky. It can also be used to eliminate or reduce reflections from non-metallic surfaces such as water or glass. It must be rotated in 

front of the lens until you achieve the desired effect. Linear polarizers can be used with some cameras, but can interfere with the metering and autofocus systems of many models. Circular polarizers avoid such problems.

Polaroid camera Instant camera that produces an image within minutes of exposure. Each print contains its own processing chemicals and is automatically fed out of the camera, whereupon the processing chemicals develop the print.

Polaroid film There are two types of polaroid film: the first is used in a Polaroid camera, while the second is used in an interchangeable Polaroid back that can be added to specially designed SLR, medium-, and large-format cameras. This second type is used by professional photographers to preview the shot before re-taking with the desired film.

Portrait lens Short telephoto lens with a focal length of about 90mm (for a 35mm camera).

Posterization Technique where the number of colors or tones in a photograph is drastically reduced. Instead of gradual changes in density and color, the picture is made up of bands of identical color – similar to a painting-by-numbers picture. The effect can be achieved in the darkroom, but is produced far more easily using digital image manipulation software. Posterization can also be an unwanted side-effect of digital imaging – caused by over manipulation of the image.

ppi (points per inch) Also known as pixels per inch, ppi is an indication of the resolution of a digital image produced by a digital camera or scanner.

Predictive autofocus Autofocus setting where the focus is not only constantly adjusted until the shutter is actually fired, but is also adjusted during the delay between pressing the trigger and the shutter actually opening. The camera can therefore track moving subjects more accurately. A common feature on autofocus SLRs.

Preview button See Stop-down button.

Primary colors In a photographic context, the term usually refers to the colors blue, green, and red. In terms of painters’ pigments, the primary colors are blue, yellow, and red.

Prime lens See Fixed focal length lensPrinting-in See Burning-in.
Pulling See Downrating.

Push processing Technique for increasing the sensitivity of a film. The film is exposed at a higher-than-normal ISO rating, and is then developed for longer to compensate. 


RAM (random access memory) A computer’s working memory – the storage area it uses whilst working on files and processing information. Digital manipulation programs can require more RAM than many other computer programs, particularly when handling large image files.

Rangefinder Manual focusing system that superimposes two views of the subject. When they coincide, the subject is in focus.

Rebate Non-image area on a film in which the frame numbers and, on some films, the sprocket holes are located.

Rear curtain sync Facility found on some SLRs and flashguns that synchronizes the flash output with the moment when the second shutter curtain is about to close. Normally a flashgun synchronizes with the point where the first shutter is fully open. The facility gives more natural-looking images when using slow synch flash with a moving subject, as the blurred after-image created by the ambient light appears behind the line of movement, rather than in front of it.

Reciprocity failure Loss of sensitivity of a photographic emulsion when given either a very brief or a very long exposure. Color material may also experience uncorrectable shifts in color balance.

Red-eye Fault caused by light reflected from a subject’s eyes when exposed by flash. A particular problem with cameras with built-in flash with telephoto zoom settings – as the angle between flash and lens axis is narrow.

If possible, move the flash unit to one side or bounce the light before it reaches the subject. Some cameras have settings that use a preflash to reduce the size of the irises of the subject’s eyes, to minimize the problem. Another solution is to move closer to the subject, using a wider lens setting.

Reflected light reading An exposure reading taken by measuring the amount of light reflected back from the subject toward the camera. All TTL (through-the-lens) exposure- measuring systems take a reflected light reading. See also Through-the-lens metering.

Reflex camera Camera design that uses a mirror between the lens and focusing screen to correct the upside-down image produced by the lens.

Reflex lens See Mirror lensResolution The ability of a lens, film or

digital imaging device to record fine detail.

Retouching Removing blemishes and/or changing the tonal values of negatives, slides, prints or digital images. 


RGB Red, green, and blue. The three colors

used by digital cameras, scanners, and computer monitors to display or record images. Digital images are therefore usually RGB models – but they can be converted to other color models (such as CMYK).

Ring flash Circular flash lighting unit that fits around the outside of the front of the lens. Most often used in close-up photography to produce localized, shadow-free illumination.

Roll-film camera See Medium-format camera


Safelight Low-output darkroom light filtered through an appropriate color (orange is usual) so as not to affect unexposed printing paper. Black and white printing paper is not affected by safelighting, but most films and color papers will be, so different colored filters are used.

Scanner Device that converts a physical image into a digital one.

Sheet film Large-format film cut to a specific size rather than in roll form. Each sheet is used for just one photograph.

Shift lens Lens in which some elements can be shifted vertically or horizontally off- center, to overcome the type of problem encountered when a camera is tilted (to include the tops of tall structures, for example). Also known as a perspective control (PC) lens.

Shutter Device that controls the moment of exposure and the length of time light is allowed to act on the film to produce an image. See also Between-the-lens shutter and Focal-plane shutter.

Shutter priority Type of semi-automatic exposure system whereby the photographer sets the shutter and the camera selects the corresponding lens aperture to ensure correct exposure of the scene.

Single lens reflex (SLR) Type of camera in which the viewfinder image shows the subject through the same lens that will be used to expose the film or imaging chip. A mirror is used to reflect the image to the viewing screen, which moves out of the way when the picture is taken.

Skylight filter Pale amber filter that can be used with color film to introduce a slight, natural-looking color-cast. Useful with cold- looking scenes and to counteract the tendency of some films to produce a blue cast in shadow areas.

Slave unit Fires additional synchronized flashes when the principal flash lighting unit connected to a camera fires. 

Slide Positive film image designed to be viewed by projection. Also commonly known as a transparency or a positive.

Slow film See Film speed.

Slow lens See Lens speed.

Slow sync flash Technique where a slow shutter speed is combined with a burst of flash. The flash usually provides the main illumination, but the ambient light creates a secondary image that can be useful in suggesting movement. The technique can also be used to ensure that the background receives more exposure than it would otherwise have done.

SLR See Single lens reflex.
Snoot Type of flash head used to direct a

narrow beam of light over a small area.

Soft-focus lens Lens designed to produce a slightly soft image, with not all in-focus elements critically sharp. A portrait lens may also be a soft-focus lens.

Solarization Complete or partial reversal of an image, caused by massive overexposure to white light. The effect can easily be mimicked using digital manipulation software.

Spot meter Type of exposure meter with an extremely narrow angle of view. A spot meter is used to take a light reading from a specific part of a subject.

Spotlight Unit that produces a strong beam of light, which can easily be trained on a subject.

Spotting Removing blemishes or small unwanted areas of detail on a print using a paintbrush and dyes, watercolors, or graphite. Similar correction is possible with digital images using manipulation software, most usually with the aid of the clone tool.

Standard lens Lens with a focal length approximately equal to the diagonal of the image area of the format with which it is used. With 35mm format film the standard lens is 50–55mm, and an 80mm lens with 6 x 6cm medium format film. A standard lens reproduces about as much of a scene as you would see with the naked eye (excluding peripheral vision).

Starburst filter Special effects filter that produces starlike patterns around the sources of light in a photograph.

Stop Another name for aperture. See Aperture.

Stop bath Chemical solution (usually weak acid) that halts the action of film or paper developer and neutralizes any developer residues, so preventing contamination of other processing chemicals.

Stop-down button Manual control that closes down the aperture to that selected for 

exposure. The photographer can then judge depth of field on the focusing screen. Also known as a preview button.

Stopping down Closing down the aperture.

Strobe light Low-output flash light that is capable of delivering many thousands of flashes per second.

Studio flash Large flash units, often connected to heavy-duty power packs and mounted on adjustable stands, and designed to illuminate large areas of a photographic studio or for use on location.


Technical camera See View camera.

Telephoto lens Lens with a focal length that is longer than the standard lens for the format being used. See Standard lens.

Test strip Strip of printing paper or film that is given a range of trial exposures.

Through-the-lens metering A type of light- measuring system used commonly in reflex cameras to measure the light that is reflected from a subject and then passes through the lens. Commonly abbreviated to TTL.

TIFF (Tagged Image File Format) Digital image format used to record files with maximum available detail. File sizes can, however, be large.

TWAIN (technology without an interesting name) Piece of software, similar to a driver, that allows you to control a scanner, or similar computer peripheral, from another application – such as a digital image manipulation package.

TLR See Twin lens reflex.

Tonal range Range of shades of gray, between the extremes of black and white, which can be distinguished in a photograph.

Tone An area on a print or negative that has a uniform density and that can be distinguished from other lighter or darker parts.

Transmitted light Light that passes through a transparent or translucent material.

Transparency See Slide.
Tripod Camera-steadying device consisting of

three legs and some form of mounting system to hold the camera. Tripod legs are extendable so that the camera height can be adjusted, and most also have an extendable central column (on top of which the camera is mounted) for finer height adjustments. The two most commonly available camera-mounting heads are ball-and-socket and pan-and-tilt types. 

TTL See Through-the-lens meteringTungsten-balanced film Film designed to

reproduce correct subject colors when exposed in tungsten light. If exposed in daylight without the appropriate correction filter over the lens, subject colors will appear unnaturally blue. See also Daylight-balanced film.

Twin lens reflex (TLR) Type of medium- format camera that uses two lenses of identical focal length mounted one under the other on a lens panel. The top lens is used for viewing and focusing and the bottom lens for taking the picture. Some models have interchangeable lenses, which are changed as paired units. 


Ultra-violet (UV) filter Colorless filter designed to remove excessive ultra-violet from the light passing through the lens. A UV filter may be left on the lens all the time to protect the lens from dirt, knocks, and scratches. UV filters do not affect exposure.

Ultra-violet light Part of the electro-magnetic spectrum beyond visible blue. In distant scenes, such as mountainous areas, ultra- violet radiation increases the effects of aerial perspective by creating a blue haze. Ultra- violet effects can be minimized by using an ultra-violet filter.

Underexposure Occurs if a film or imaging chip receives too little light, causing dark pictures and a reduction in subject contrast.

Uprating Exposing film as if it is more sensitive to light than its ISO rating indicates. Allowances for uprated film have to be made during development. Also known as pushing.

Unsharp mask (USM) A facility provided on digital image manipulation programs that allows you to sharpen an image. Takes its name from a printing process, where a soft- focus negative is sandwiched with the original in order to increase edge contrast.

UV filter See Ultra-violet filter. 


Vanishing point Point at which parallel lines appear to converge in the distance. Used by artists to give realistic perspective in a two- dimensional representation.

View camera Large-format camera, using individual sheets of 5 x 4in (12.7 x 10cm) film or larger, with a lens panel mounted on a flexible bellows and a ground-glass screen at the image plane for viewing and focusing. 

There are two main designs. The monorail camera allows a full, independent movement of film and lens planes – allowing a high degree of control over image distortion, perspective and depth of field. However, they are heavy and cumbersome so are best suited to studio use where they can be supported on a heavy stand. Field cameras have a baseboard to support the bellows and are slightly more portable. Also known as technical, field, or baseboard cameras.

Viewfinder Viewing system that allows a camera to be aimed and focused accurately. The viewfinder often contains exposure- related information around the edges of

the screen.

Viewpoint In photography, the position from which the picture is taken in relation to the subject. Very small changes in camera viewpoint can result in considerable differences in finished prints or slides.

Vignette Gradual fading of a photographic image to white or black. The effect can be achieved in the darkroom either by holding light away from the edges to create a white vignette (see Dodging) or by giving a large amount of extra exposure to the edges to create a black vignette (see Burning-in).

Visible spectrum The part of the electro- magnetic spectrum between infra-red and ultra-violet that is visible to the naked eye. 


White balance System by which a digital camera measures the color temperature of a light source and then corrects it so that the whites, and therefore all the other colors, appear normally to the human eye.

Wide-angle lens Lens with a focal length shorter than the diagonal of the film format with which it is used. Commonly used wide- angle lenses for 35mm-format cameras include 35mm, 28mm, and 24mm focal lengths. Lenses wider than this may show signs of barrel distortion. 


X-ray fogging A gray veil produced when unprocessed photographic emulsions are exposed to excessive X-ray radiation. This can occur as a result of baggage screening at airports, but modern systems use X-ray dosages that should be safe for most emulsions. Repeated screenings of

films, especially fast films, may have a cumulative effect. 

X-sync socket External socket found on some cameras that accepts a cable connecting the shutter to an electronic flashgun used off- camera. It ensures that the firing of the flash is synchronized with the opening of the shutter. 


Zoom lens Type of lens designed so that groups of internal elements can be shifted in relation to each other to produce a range of different focal lengths. See also Fixed- focus lens