Glossary "A"

The base for APS film emulsions. Its a strong material that it accepts film emulsions evenly and, with a thickness of just 90 microns its 30% thinner than the acetate base used in conventional 35mm emulsions.

A device found in digital cameras and scanners that converts analogue picture information (continuous tone subject) to digital data (digital image).

Optical problem in a camera lens that produces slight errors in subject appearance, usually noticeable in small details.

Image which does not depict something in a literal nor complete way. For example, a close-up which removes the original's form and function, else an image with the original so obscured as to make other interpretations very apt.

A chemical ingredient of film or paper developers that's often referred to as an activator and speeds up the developing agents. It's usally an alkali such as sodium carbonate, borax or sodium hydroxide.

A chemical substance such as a stop bath or fixer with a pH below 7 that's used to stop film or paper development.

A camera with active autofocusing uses an infrared beam to determine how far away the subject is. This is fine providing the subject isn't behind glass, because the beam will think the glass is the subject. The system is also flawed when the subject is beyond the range of the infrared, then the camera usually switches to an infinity mode.

A measure of how the step from high to low density reproduces in a developed film that has been exposed to a high contrast subject. A high acutance developer produces a steeper step from low to high density and, as a result, makes the image appear sharper

A camera lens accessory that fits onto the filter thread of a lens to allow a filter system holder to be attached. Other types are available that step-up or step-down from the actual lens filter diameter to allow other size filters to be used.

Process that exposes different amounts of red, green and blue primary coloured light onto colour printing paper to create a new colour.

A new film format developed and introduced by Minolta, Nikon, Fuji, Kodak and Canon back in 1996.The system was developed to make it easier to load into cameras and offers many processing benefits. For more information, see "APS"

Where the camera measures the amount of light required for a scene and adjusts the exposure to suit.

A button or lever on the camera or exposure meter used to lock the automatically measured light reading into a memory while you recompose.This is ideal for backlit subjects because you can move closer to the subject, take a reading without any background in the view, lock the exposure and move back to the original position to take the photo.It's also fine for landscapes when there's an expanse of bright sky. Point the camera down to the ground, lock the exposure, recompose and shoot.Use this to bias the exposure to one area of the scene or to maintain a consistent reading when lighting conditions are variable.

An infrared or bright light beam that fires from the camera to the subject to determine camera to subject distance or to assist autofocusing in low light.

A mode to lock the focus to a predetermined point. Useful when the subject is moving fast because you can take the photo as it reaches a certain point or when other influences could affect the focusing such as shooting through glass or in crowded locations.

Digital images are made up of square pixels and when the image is low resolution there are fewer pixels per inch. This creates a rough step-like appearance that is most noticeable on diagonal straight edges. This staircase effect is often described as "jagged".

Available light - this can be any kind of light that's already there, such as daylight or artificial light - as opposed to light the photographer adds with a flash gun or other photographic lighting unit.

A measurement of ambient light.

The range, usually indicated as a range of EVs (exposure values), that the meter can work in. The larger the range the more versatile the meter. An ISO film speed is usually quoted to indicate what the measurement scale is based on.

Responsible for supplying the speed rating of photographic film. Doubling the ASA number indicates twice the light sensitivity. ASA was replaced with ISO in the 1980s.

Used to describe the stereo photography method of viewing images using deep red and green spectacles. The two pictures have their red and green content displaced which gives the three-dimensional appearance when viewed through the special eyepieces.

An optical design that gives different image magnification in the horizontal and vertical planes creating a widescreen image.

The amount of a distant scene that can be viewed using a camera lens. This varies with the focal length of the lens and film format.

A figure generated to indicate the light sensitivity of printing paper. Not to be confused with the ANSI computer character standard.

A method of smoothing out pixels' jagged edges using software.

A light-absorbing dye thats present in the film to prevent reflections and light spread that would create a halo around bright highlights. The dye disappears during processing.

A hole in the lens that adjusts in diameter, similar to the way the pupil of an eye works. This controls the amount of light reaching the film or CCD to record an image. Every different diameter opening has a number which indicates the size - it equals the focal length of the lens divided by the diameter of the aperture. These numbers are also called stops. See f/number.

A mechanical lever or electronic button used to close the lens aperture down to the actual exposure setting so depth of field can be previewed.

An auto-exposure mode where you select the required lens aperture and the camera sets the necessary shutter speed, to give the correct exposure based on the auto meter reading. This mode is ideal for landscape and still-life photography where maximum depth-of-field is required. It's either indicated on the camera as AP (aperture priority) or AV (aperture value).

A ring that is situated near the lens throat on all manual focus lenses and some autofocus models that adjusts to control the amount of light reaching the film or CCD when recording an image. Cameras that don't have an aperture ring often have an electronic control to adjust the aperture either automatically or manually.

See Aperture priority exposure.

A special design of lens that is highly corrected to avoid chromatic aberration by bringing the three blue, red and green wavelengths to one point of focus rather than the usual blue and green of an achromatic lens. Because red is also brought to the same point of focus, you don't need to refocus when taking infrared pictures with this type of lens.

Advanced Photo System, a camera and film system designed jointly by Kodak, Fuji, Nikon, Canon and Minolta. The film cartridge, with a slightly smaller film than 35 mm film, is as easy to load as a battery film as it slots effortlessly into a chamber on the camera, and can be exchanged for another film without having to finish the roll. It also has a status indictor on one end showing if the film is unused, partially used, used but unprocessed or processed. So you won't hand in an unexposed roll for processing or put a film through the camera twice and double expose everything. The system allows the photographer to have his settings recorded on the back of his prints, which is automatically done by the processing lab. Although a few APS SLR models were made by Canon and one other manufacturer, most APS cameras tend to be compact and easy to use, but they are often less versatile than 35mm cameras at equivalent price points. The APS system is now regarded as an interim product, used only by consumers, which was popular for a short time, until better compact cameras became available at affordable prices. Most manufacturers have discontinued production of APS cameras. APS film is still available here and there, and processing labs still accept APS film.

Advanced Photo System type-C should not be confused with the Advanced Photographic System (APS) camera/film system, since the former is digital and the latter is analogue. APS-C is a type of image sensor found in certain digital single lens reflex (DSLR) cameras. These sensors are smaller than the ones used for the conventional 36 mm x 24 mm (35 mm) sensor SLR cameras (also called full frame DSLR cameras). Being smaller causes a 1.x multiplier for the effect of the focal distance of the lenses, in comparison with the effect of those lenses on conventional 35 mm film SLR cameras or full frame digital SLR cameras. Several manufacturers produce cameras with an APS-C sensor and some even make lenses especially for them. These lenses are found in the Canon EF-S, Nikon DX, Pentax DA and Sigma DC ranges, to name the most popular ones. The most common multiplier ratios are 1.6 (Canon), 1.5 (Nikon, Fuji, Sony, etc.), 1.3 (Canon). (1.3 crop sensors are also sometimes called APS-H.) Most manufacturers not only produce cameras with these cropped sensors, but also offer DSLR cameras with full frame sensors.

Extra steps are taken when developing and printing to ensure the most stable image is made.

A development by Dr. Mike Ware of Kallitype and Van Dyke Brown, Argyrotype produces brown silver prints of subtle graduation on plain artist's paper. The sensitiser, which can last a year or more if correctly stored, should be spread evenly on the print using a glass rod. After a few minutes to allow it to soak in, the print should then be dried for ten minutes at 40C or for half an hour at least at room temperature. A contact printing time of 5-10 minutes under the sun or a good source of UV light is normal. After exposure, develop and clear the print in gently running water for around 5 minutes, and then use a fixing solution for 3 minutes. At this point the colour will intensify, changing from red to a deep brown, which can be turned more blackish-brown by ironing dry at this stage.

Irregular flaws in image colour or sharpness caused by CCD problems, noise or compression.

Used to describe any continuous man made light source such as tungsten and fluorescent lighting.

A code for exchanging information between data processing systems and peripherals such as postscript printers.

A lens element that doesn't form part of a sphere. This is physically difficult to manufacture as most grinding/polishing equipment operates with a spherical action. This sort of lens is often moulded out of plastic or coated onto a glass element.

A high speed Internet connection that is many times faster than a normal modem. It allows your normal or digital phone line to be used, but you need additional hardware installed to connect to the service. Some telecom exchanges also need to be set.

A series of photos taken rapidly by the camera each giving a slightly different auto exposure.

Early colour transparency system, using a mosaic of additive colour filters.

The camera uses an infrared beam or the subject's contrast to measure the camera to subject distance and focuses the lens automatically