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- A.S.A.
- An absolute term indicating a film's sensitivity to light. The letters stands for American Standards Association . The term as been replaced by ISO standing for International Standards Organization.
- A/D converter
- A device used to convert analog data to digital data. Analog data is continuously variable, while digital data contains discrete steps.
- A3
- Paper size for documents measuring up to 11.7" x 17".
- A4
- Paper size for documents measuring up to 8.27" x 11.69".
- A5
- Paper size for documents measuring up to 5.83" x 8.28".
- Aberration
- (1) Something that prevents light from being brought into sharp focus, disenabling the formation of a clear image. (2) Lens flaw - the inability of a lens to reproduce an accurate, focused, sharp image. Aberration in simple lenses is sub-categorized into seven types: Astigmatism - lines in some directions are focused less sharply than lines in other directions, Chromatic aberration or Axial chromatic aberration - different wavelengths of light coming into focus in front of and behind the film plane, resulting in points of light exhibiting a rainbow-like halo and reduction in sharpness, Coma - the image of a point source of light cannot be brought into focus, but has instead a comet shape, Curvilinear distortion - distortion consisting of curved lines, Field curvature - the image is incorrectly curved, Lateral chromatic aberration also known as Transverse chromatic aberration - variation in the magnification at the sides of a lens (this aberration type used to be termed “lateral colour”), Spherical aberration - variation in focal length of a lens from center to edge due to its spherical shape - generally all parts of the image, including its center. The effects of lens aberration usually increase with increases in aperture or in angle of field.
- Abort
- To stop a program while its running. Aborting can be initiated by the user or by the program itself.
- Abrasion marks
- On the emulsion surface of the film are caused by scratching. It can be due to traces of dirt trapped between layers of film as it is wound on the spool, dirt in the film holder or grit on the pressure plate
- Absolute colorimetric
- A rendering intent that aims to maintain colour accuracy at the expense of preserving relationships between colours, used to predict how images will appear when printed on paper or other substrate with a distinct colour cast, such as newsprint. With absolute colorimetric rendering intent, colours that falls inside the destination gamut remain unchanged, while out-of gamut colours are clipped. Colours are not scaled to the destination white point.
- Absolute white
- In theory, a material that perfectly reflects all light energy at every visible wavelength. In practice, a solid white known spectral data used as the " reference white " for all measurements of absolute reflectance.
- Absorption
- Occurs when light is partially or completely absorbed by a surface, converting its energy to heat.
- Abstract
- In the photographic sense, an image that is conceived apart from concrete reality, generally emphasizing lines, colours and geometrical forms, and their relationship to one another.
- Accelerator
- Is a chemical added to a developer solution to speed up the slow working action of the reducing agents in the solution.
- Access
- To acquire data into a computer system, typically from a storage device or from an input device.
- Access time
- The time required for a data storage device to locate and retrieve data.
- Accessory
- An add-on to a computer; a peripheral like a mouse or a printer. Something not central to the computer's operation.
- Accessory shoe
- Is a metal or plastic fitting on the top of the camera which support accessories such as viewfinder, rangefinder, or flash gun. The term " hot shoe " is sometimes uses as an alternative to accessory shoe.
- Accuracy
- The extent to which a machine vision system can correctly measure or obtain a true value of a feature. The closeness of the average value of the measurements to the actual dimension.
- Acetate base
- Non-inflammable base support for film emulsions which replaces the highly inflammable cellulose nitrate base.
- Acetate filters
- A coloured piece of acetate sheeting used over light sources as opposed to optical quality filters used over camera lenses.
- Acetic acid
- Is a chemical used for stop bath which stops the action of the alkaline developer.
- Acetone
- A solvent chemical used in certain processing solutions that contain materials not normally soluble in water.
- Achromatic
- Is a lens system that has been corrected for chromatic aberration.
- Acid free
- Specially prepared mounting boards, album pages, tissues, and storage boxes designed to house prints for maximum archival permanence.
- Acid hardener
- Is a substance used in acid fixer to help harden the gelatin of the emulsion.
- Acquire
- The opening up and importing of files into a given software application. The term is applied differently with in different types of software. With imaging software it is most often done through a twain interface or plug-in mini-application.
- Acquire module
- A Graphics Program plug-ins, which provide direct access to scanners, digital cameras, video sources and other file formats.
- Acrobat reader
- Adobe's electronic document format. Documents can be created from within a word processor, from postscript, or from scanned pages. The documents are highly portable, yet maintain the look of the original. Acrobat is especially useful in this area because Adobe makes the reader available for free.
- Action
- A Photoshop command sequence you can record and replay to automate recurrent imaging tasks.
- Activator
- A solution used in rapid access processors to activate developing agents present in certain emulsions of photographic products.
- Active-Matrix Display
- A type of flat panel LCD display used in laptop and portable computers. Active matrix displays produce a superior image to passive matrix displays.
- Actual size
- The size of an image when it was scanned ( not enlarged or reduced in area or viewing perspective ).
- Acutance
- A measure of the sharpness with which the film can produce the edge of an object.
- AD conversion
- Analog-Digital Conversion. In order to process a continuous analog signal in a computer (e.g. a photo), it must first be digitized, which means, converted into a specific mathematical format of binary code. Pictures are usually digitized with the help of a digital camera or a scanner.
- Adapter ring
- Is a circular mount, available in several sizes enabling accessories such as filters to be used with lenses of different diameters.
- Adaptive compression
- A type of compression software commonly used to back up files. The method of compression changes with the type of file, and is not recommended for photographic images because it may destroy original data.
- Additive colour model
- The color model in which colours are produced by combining various percentages of red, green, and blue light. In the additive colour model, white is produced by mixing 100% of each primary, whereas black is produced the absence (i.e., 0%) of each primary. The additive colour model is used by computer monitors to produce their display.
- Additive palette
- This is a set of colours selected to represent, as closely as possible, the colours in the original source image.
- Additive primary colours
- Red, Green, Blue; The 3 colours used to create all other colours when direct, or transmitted light is used .They are called additive primaries, because when those are superimposed they produce white.
- Addressable resolution
- The maximum number of pixels an imaging device is capable of manipulating, and not necessarily the same amount the monitor is capable of displaying..
- Adobe colour engine (ACE)
- The colour management model created by Adobe Systems, Incorporated that is the default conversion engine used for ICC colour-managed colour conversions with Adobe applications.
- Adobe gamma
- A utility for calibrating and characterizing a monitor to produce an ICC profile for use in Adobe Photoshop and other ICC-aware applications. Although still bundled with Windows versions of photoshop, it has been replaced on the Macintosh by the calibration routine built into Apple ColorSync.
- Adobe RGB (1998)
- The RGB working space created by Adobe Systems, incorporated that provides a fairly large gamut of colours and is well-suited for documents that will be converted to CMYK
- Advanced Photo System; APS
- A new standard in consumer photography developed by Kodak and four other System Developing Companies - Canon, Fuji, Minolta and Nikon - based on a new film format and innovative film, camera and photofinishing technologies. Generally, APS cameras are more compact in size, weight and enbodied most of the latest and most advance technologies available. There are options in various sizes of print out and it will even provide a thumbnail prints (Contact sheet) for you to select or preview prior to actual printing. There have a different series of lenses and some of the 35mm format AF lenses can even be shared (With limitation or effective focal length will increased). You can say, it is a different system camera all together. So much for the brighter side, but there are drawbacks as well and it is not that economical as I originally thought it supposed to be.
- AF
- Abbreviation for " Autofocus ".
- AF illumination lamp
- An infrared beam that the camera fires to assist in auto focusing.
- AF sensor
- The sensor used to detect focus in cameras equipped with an autofocus function. Algorithm - a rule or process (often mathematical) used by a computer to make a decision or series of decisions.
- Agitation
- Keeping the developer, stop bath, or fixer in a gentle, uniform motion while processing film or paper. Agitation helps to speed and achieve even development and prevent spotting or staining.
- AGP ( accelerated graphics port )
- A new bus specification that enables personal computers to quickly display 3-D graphics.
- Air bubbles
- Clear areas---usually round---on film, produced by bubbles of air trapped on the film during development. They are caused by insufficient agitation while developing the film.
- Airbrush
- A digital tool which gives the effect of spraying a paint / air mixture over a image. Most graphic packages incorporate an assortment of brushes that are user definable.
- Algorithm
- The specific process in a computer program used to solve a particular program.
- Aliasing
- When a line or any shape (curve, circle or font text character) is painted, and its edges are not perfectly horizontal or vertical, some pixels are only partially covered. The resulting jagged-edged lines are said to be aliased. Aliasing gives lines a "stair-step" or "jaggie" appearance. The greater the number of dots or pixels on your display, the higher the display resolution, and the less noticeable aliasing is to the human eye.
- Alkalinity
- Denotes the degree of alkali in a solution, measured in pH values. All values above pH 7 are alkaline.
- Alpha
- The degree of opacity of an image in computer graphics. Not the same as luminance.
- Alpha channel
- An extra 8-bit, grayscale channel in an image - often used for creating masks to isolate part of an image.
- Alpha Chip
- A Digital Equipment Corporation produced RISC chip that is known for its processing speed.
- Alpha Chip Analog
- An electronic signal, tone or other measure that is continuously variable in its level.
- Alphanumeric
- A combination of letters and numbers.
- Ambient light
- Existing light surrounding a subject; the light that is illuminating a scene without any additional light supplied by the photographer. " Available light " and " existing light " are two other terms that mean the same thing.
- Ambient temperature
- Crudely, room temperature. Some photographic chemicals can be used "at ambient" (with appropriate correction of processing times) while other types need to be heated or cooled to a specific temperature required by a particular process.
- Amidol
- Soluble reducing agent which works at low pH values
- Analog to digital (A/D) converters
- A device which converts an analog signal into a digital signal. Complex waveforms are converted into simple strings of numbers.
- Analogous colours
- Colours that are next to each other on the colour wheel.
- Analogue
- Continuous signals; data presented or collected in continuous form. This data is shown on an instrument that can change constantly. For example, speedometers or thermometers are analog devices. Analog signals can represent many different real-world things, like video, audio, (voice, music) and physiological waveforms (ECG, heartsounds, respiration).
- Anamorphic sizing
- Unequal scale change in the horizontal and vertical direction of a scanner. This enables the scanner to adjust the ratio in the horizontal and vertical direction.
- Anamorphic sizing
- Unequal scale change in the horizontal and vertical direction of a scanner. This enables the scanner to adjust the ratio in the horizontal and vertical direction.
- Anastigmat
- Is a compound lens which has been corrected for the lens aberration " astigmatism ".
- Angle of flash coverage
- The measurement in degrees of the angle formed by lines projecting from the center of the flash to the extremities of the field of coverage.
- Angle of incidence
- When light strikes a surface it forms an angle with an imaginary line known as the : normal, which is perpendicular to the surface. The angle created between the incident ray and the normal is referred to as the angle of incidence.
- Angle of view
- Is the maximum angle of acceptance of a lens which is capable of producing an image of usable quality on the film.
- Angular field
- The angle subtended at the lens by the diameter of the largest circle within which the lens gives an image of acceptable sharpness and even illumination.
- ANSI
- Is a rating for photographic materials devised by the American National Standards Institute.
- Anti-aliasing
- The process of reducing Stair-Stepping by smoothing edges where individuals pixel are visible.
- Anti-fogging agent
- Constituent of a developer that inhibits or reduces fogging during development.
- Antihalation backing
- Is a dye used on backs of most films capable of absorbing light which passes through the emulsion. This way it reduces the amount extraneous light can be reflected from the camera back through the emulsion.
- Antireflection coating
- One or more thin layers of refractive material ( often magnesium fluoride ) coated upon the surface of a lens to minimize surface reflection. It is deposited on the lens by vaporization of the metal in vacuum.
- Aperture
- The iris in the lens through which light passes to exposed the film. The higher the number, the smaller the amount of light that hits the film.
- Aperture control
- The ring on the camera lens (a pushbutton on some models) that, when turned, adjusts the size of the opening in the iris diaphragm and changes the amount of light that reaches the film.
- Aperture lens opening
- The opening in a camera lens through which light passes to expose the film. The size of aperture is either fixed or adjustable. Aperture size is usually calibrated in f-numbers. The larger the number, the smaller the lens opening.
- Aperture priority
- An exposure mode on an automatic or autofocus camera that lets you set the aperture while the camera sets the shutter speed for proper exposure. If you change the aperture, or the light level changes, the shutter speed changes automatically. Apart from the sport or action arena, aperture priority is the most common & effective automatic preference in photography. It can also explained as automatic exposure system in which the lens aperture is set by the photographer, and the camera sets the shutter speed. Can be used in the stop-down mode with any lens that does not interfere with the metering system.
- Aperture ring
- A ring, located on the outside of the lens usually behind the focusing ring, which is linked mechanically to the diaphragm to control the size of the aperture; it is engraved with a set of numbers called f-numbers or f-stops.
- Aplanat
- Is a lens which has been corrected for spherical aberration.
- Apochromatic
- The inability to bring light of all colours to the same plane of focus is known as chromatic aberration. Light refraction is a function of wavelength, and as such each colour is normally brought to as lightly different plane of focus. By using complex lens designs, special glass materials and coating, designer can bring the colours within a much narrower focus. When such a lens is designed it is said to be Apochromatic.
- Application
- A computer software program designed to meet a specific need.
- APS
- An abbreviation for Advanced Photo System. It is a film cartridge system that magnetically records all picture data for each frame of film. This data is then used by the photo finisher to provide you with better pictures and new services that can't be found with traditional film cameras.
- Archival Image
- An image meant to have lasting utility. Archival images are of a higher resolution and quality than the digital image to the user on-screen. The file format most often associated with archival images is TIFF, or Tagged Image File Format, as compared to on-screen viewing file format, which are usually JPEGs and GIFs.
- Archival Processing
- Processing designed to protect a print or negative as much as possible from premature detorioration caused by chemical reactions.
- Archival scans
- Digital images serve as surrogates of the original. At this point in time, there is no such thing as an Archival or Preservation scan that acts as an exact replica or replacement of the original, as it is not yet possible to record every piece of information found in the original with today's scanner technology.
- Array camera
- A digital camera that uses a large CCD chip to sense the entire image at one time rather than scanning the image one row of pixels at a time.
- Array processor
- A specific portion of a large computer system that assists processing data quickly. An array processor is sometimes capable of performing several operations simultaneously.
- Artifact
- Colour faults or line faults that visibly impact the image negatively. Any visible degradation of an image caused by scanning, editing or compressing the image. Often artifacts are regular or repeating, rather than random.
- Artificial Intelligence
- The use of computers to solve problems and process information in ways that approximate human thought.
- Artificial light
- Light produced by electricity instead of by nature. Generally the term refers to light specially set up by the photographer, such as flash or photo lamps. Photographic emulsion have different sensitivity to daylight and artificial light, and film may be rated for either type.
- ASCII
- An acronym for the American Standard Code for Information Interchange is a ANSI binary-coding scheme consisting of 128 seven bit pattern for printable characters and control of equipment function. ASCII is the basis for information exchange between many computer system.
- Aspect ratio
- The ratio of width to height. Used in the imaging industry to define applicability of an image to fit a page, screen, monitor, or frame. For example, a 35mm frame is 3:2, a TV is 4:3, and HDTV is 16:9.
- Aspherical lens
- A lens whose curved surface does not conform to the shape of a sphere; lenses are usually ground or molded with spherical surfaces; because a spherical surface lens has difficulty in correcting distortion in ultra-wideangle lenses or coma in large-aperture lenses brought about by spherical aberration, an aspherical lens is used.
- Aspherical surface
- A lens surface that possesses more than one radius of curvature. The aspherical elements compensate for the multitude of lens aberrations common in simpler lens designs.
- Astigmatism
- A lens aberration or defect that is caused by the inability of a single lens to focus oblique rays uniformly. Astigmatism causes an object point to appear as a linear or oval-shaped image.
- Attachment
- A file, such as a photograph, sent along with an e-mail message so it can be viewed or saved at the recipient's end.
- Auto balance
- A system for detecting errors in colour balance in white and black areas of the picture and automatically adjusting the white and black levels of both the red and blue signals as needed for correction.
- Auto bracketing
- A system that automatically makes a series of exposures at different exposure settings when the shutter is released, to increase the chances of obtaining a correctly exposed image.
- Auto Exposure Bracketing
- Auto Exposure Bracketing performs automatic exposure bracketing with varied shutter speed and/or aperture.
- Auto exposure lock
- A push-button, switch, or lever that locks in exposure after the initial reading has been made, regardless of a change in camera position or light conditions after the lock is activated. Release of the lock button returns the exposure system to normal. Useful for making highlight or shadow readings of select portions of the frame, and an essential feature for critical exposure control with automated cameras.
- Auto levels
- This is a very basic automatic correction technique employed by scanning and image processing software. Usually, the process takes an Integrated reading of the image and attempts to adjust the image by targeting a neutral scale for all values. This only works in a perfectly neutral image and often Auto Levels alone is insufficient to perform quality image optimization.
- Auto-exposure
- The camera has a built-in light meter and computer that measures available light and sets exposure for you. A feature on moderately-priced to expensive cameras. Most serious amateurs and professionals want to be able to occasionally turn off (or "override") the auto-exposure feature for those situations where they want to manually set a special exposure. Similarly, many auto-exposure cameras allow you to select "aperture-priority" or "shutter-priority" for exposure (see "exposure" to learn why). In fact many older auto-exposure cameras (from the 1970's) only featured either "aperture-priority" of "shutter-priority.
- Auto-load
- A camera that has an (alleged) simple way to load film. There are many different approaches depending on the camera. Generally, you drop the film canister into the camera, pull out an extra inch of film to a certain mark, and close the camera. Gears and a motor in the camera then grab the film and advance it to the spool. Avoids the old hassles of getting the end of the film attached to the take-up spool. Found on nearly all auto-wind cameras. A handy feature that speeds up changing film.
- Autochrome
- Early commercial colour photography process in which the principals of additive colour synthesis were applied.
- Autofocus
- Device used in certain cameras, projectors and enlargers that focuses the image automatically.
- Automatic exposure setting
- A system that automatically sets correct exposure by linking a camera’s exposure meter with the shutter or aperture or both. There are three main types: aperture priority, when the photographer sets the aperture and the camera selects the appropriate speed; shutter priority, when the photographer chooses the speed and the camera sets the correct aperture; and programmed, when the camera sets both aperture and shutter speed. Aperture priority is advantageous when you want to control depth of field; shutter priority comes into its own particularly in action photography; and programmed exposure can be useful when the photographer has to react quickly. Abbreviated AE.
- Automatic flash
- An electronic flash unit with a light-sensitive cell that determines the length of the flash for proper exposure by measuring the light reflected back from the subject.
- Automatic focus
- A camera system that automatically brings the lens into sharp focus on the subject. Auto focus systems operate very quickly and reliably, and can usually focus more rapidly than the photographer can unaided. However, there are instances when manual focusing is preferable to automatic: for example, few auto focus systems can cope adequately when the subject is behind bars, such as animals in a zoo. Abbreviated AF.
- Automatic gain control
- A process by which gain is automatically adjusted as a function of input or other specified parameter.
- Autowinder
- Film wind-on mechanism which moves the film on one frame each time the shutter is released.
- Available light
- The light that is present in a scene, either indoors or out, that is not added by the photographer. Also called ambient light or existing light.
- Axis lighting
- Light pointed at the subject from a position close to the camera's lens.
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