IPQB Glossary – International Photography Qualifications Board

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Aperture: The opening in a camera lens through which light passes to enter the camera. It is measured in f-stops, and it affects the depth of field and exposure of the photograph.

Aspect Ratio: The ratio of the width to the height of an image. Common aspect ratios include 4:3, 3:2, and 16:9, affecting how images are framed and displayed.

acutance: numerical value that correlates to some extent with subjective image sharpness – ISO 19262:2015

automatic document feeder (ADF): powered device to feed microforms, films or paper into a scanner for capture – Source ISO 12651‑1

Adobe RGB 1998: three-component colour image encoding defined in Adobe RGB (1998) colour image encoding SOURCE:ISO 12640‑4:2011

aliasing: output image artefacts that occur in a digital imaging system for input images having significant energy at frequencies higher than the Nyquist frequency of the system
Note 1 to entry: These artefacts usually manifest themselves as moiré patterns in repetitive image features or as jagged “stairstepping” at edge transitions. SOURCE:ISO 16067‑1:2003

ambient light: illumination that remains present in an area when some indicated light source (such as a specialized light, projector, or self-luminous display) is turned off
Note 1 to entry: Ambient light can be natural or artificial light. Ambient light is generally uncontrolled and can be highly variable, posing a possible risk to image quality. The level of ambient light should be minimized in relation to the level of light produced by the imaging system. SOURCE:ISO 4246:1994

array (imaging): orderly arrangement of individual sensor elements in image capture devices
Note 1 to entry: In digital imaging, there are primarily three array types: two dimensional or area arrays, one dimensional or linear arrays, and tri-linear arrays consisting of three consecutive linear arrays of red, green, and blue sensitive sensor elements. Source – ISO 19262:2015

artifact: general term to describe a broad range of undesirable flaws or distortions in digital reproductions produced during capture or data processing
Note 1 to entry: Some common forms of image artifacts include noise, chromatic aberration, blooming, interpolation, and imperfections created by compression, among others. ISO 19262:2015

aspect ratio: ratio of length to width of an object – SOURCE:ISO 13794:1999

Bokeh: The aesthetic quality of the out-of-focus areas in a photograph, typically created by using a wide aperture. It often appears as soft, circular highlights in the background.

Bracketing: A technique where multiple shots of the same subject are taken at different exposure settings to ensure one perfect exposure or to create HDR (High Dynamic Range) images.

banding (imaging): unwanted stripes or bands that occur in a digital image
Note 1 to entry: Bands are usually caused by fixed pattern noise of linear sensors in scanners or interference problems between electronic parts of a camera. ISO 19262:2015

binary image: digitized image consisting of an array of pixels, each of which has a value of 0 or 1, whose values are normally represented by dark and bright regions on the display screen or by the use of two distinct colours SOURCE:ISO 13322‑1:2004

bit depth: maximum number of discrete levels available for the digitized representation of the signal intensity, represented as a power of two
Note 1 to entry: The term can be confusing since it is sometimes used to represent bits per pixel and at other times, the total number of bits used multiplied by the number of total channels. For example, a typical colour image using 8 bits per channel is often referred to as a 24-bit colour image (8 bits × 3 channels). Colour scanners and digital cameras typically produce 24 bit (8 bits × 3 channels) or 36 bit (12 bits × 3 channels) images, and high-end devices can produce 48 bit (16 bit × 3 channels) images. A grayscale scanner would generally be 1 bit for monochrome or 8 bit for grayscale (producing 256 shades of gray). Bit depth is also referred to as colour depth. SOURCE:ISO 22493:2008

bit rate: number of bits transmitted per second SOURCE:ISO/IEC 18000‑2

bitonal (digital) image: see binary image

black point: neutral colour with the lowest luminance that can be produced by an imaging medium in normal use, measured using the specified measurement geometry SOURCE:ISO 12231:2012

blooming: phenomenon which occurs when a pixel of the solid-state imaging device is so illuminated that the number of generated electrons is greater than can be stored
Note 1 to entry: This excess of electrons can spread into neighbouring cells. As a result, the highlight areas of the scene appear increased in size on the television screen. SOURCE:IEC 808-04-03

bits per pixel: see bit depth

brightness: attribute of a visual sensation according to which an area appears to emit more or less light
Note 1 to entry: Brightness is among the three attributes that specify colour. The other two attributes are hue and saturation. SOURCE:ISO/IEC 8613‑2

Composition: The arrangement of elements within a photograph, including subject placement, background, and the overall structure of the image, to create a visually appealing and effective photo.

checkerboard: regular squared dark and bright structure on a surface like the one used on a chess board

source ISO 19262:2015

checkerboard: regular squared dark and bright structure on a surface like the one used on a chess board ISO 19262:2015

chroma: chromaticiness, colourfulness, of an area judged as a proportion of the brightness of a similarly illuminated area that appears white or hrightly transmitting
SOURCE:ISO/IEC 8613‑2

chromatic aberration: image defect caused when different wavelengths of light are focused at different distances from a lens (longitudinal chromatic aberration) or when the scale of the image at different wavelengths is different (lateral chromatic aberration)
Note 1 to entry: This results in varying degrees of sharp focus at the image sensor or shifted objects in an image depending on the colour or wavelength of light. Chromatic aberration is seen as “colour fringing,” and is most noticeable in an image at edges with high contrast. ISO 19262

chromaticity: attribute of a colour stimulus defined by its trichromatic coordinates or by its dominant or complementary wavelength and purity characteristics taken together SOURCE:IEC 723-08-33

chromaticity coodinates: ratios of each of the members of a set of CIE tristimulus values to their sum
SOURCE:ISO 105‑A08:2001

CIELAB colour space: three-dimensional, approximately uniform colour space, produced by plotting, in rectangular coordinates the component values are L, a, b* [SOURCE: ISO 5631-1:2009, 3.5]
SOURCE:CIELAB colour space is specified in CIE Publication 15

clipping: abrupt truncation of a signal when the signal exceeds a system’s ability to differentiate signal values above or below a particular level
Note 1 to entry: In the case of images, the result is that there is no differentiation of light tones when the clipping is at the high end of signal amplitude and no differentiation of dark tones when clipping occurs at the low end of signal amplitude. For digital audio, clipping occurs when the signal is restricted by the selected bit depth (which represents amplitude). In a system using 16-bit signed integers, 32 767 is the largest positive value that can be represented. If input levels are set so that excursions above that are permitted, then clipping will result and some information will be lost.
Note 2 to entry: If clipping occurs in only one or two channels of an RGB image, the hue will change instantly. For example, Caucasian skin tones can go reddish yellow when highlight clipping occurs in the red channel only.

ISO 19262:2015

clipping (black): truncation of a signal when the signal represents a tone darker than the system’s ability to differentiate
Note 1 to entry: Excessive black clipping tends to result in “blocked-up” or featureless shadows in an image.

ISO 19262:2015

clipping (highlights): truncation of a signal when the signal represents a tone lighter than the system’s ability to differentiate
Note 1 to entry: Excessive highlight clipping tends to result in “blown-out” or featureless highlights in an image.

ISO 19262:2015

codec: device or algorithm used to perform encoding/decoding and compression/decompression of the digital data
Note 1 to entry: This may be combined with converting analog signals into digital (and vice versa).

SOURCE:ISO/TR 16056‑1:2004

colorimeter: instrument for measuring colorimetric quantities, such as the tristimulus values of a colour stimulus
[SOURCE:IEC 845-05-18]
Note 1 to entry: Colorimeters are the primary device used to evaluate the colour qualities of display monitors. There are two basic types of colorimeters: tristimulus colorimeter and spectrocolorimeters.

colorimetry: measurement of colours based on a set of conventions
[SOURCE:IEC 845-05-10]

colour: sensation resulting from the visual perception of radiation of a given spectral composition
SOURCE:ISO 4618

colour accuracy: ability of an imaging system to reproduce the colours of some intended object, as specified using some colour difference metric
Note 1 to entry: The reference object against which the colour accuracy is measured can be, for example, an original scene, the colorimetry of an original scene chromatically adapted to some different adopted white, or an image file describing a reproduction on some reference medium. ISO 19262:2015

colour cast: tint of a particular colour, usually unwanted, which affects the whole of a photographic image

ISO 19262:2015

colour channel: data channel that represents some specific aspect relating to colour in an image
Note 1 to entry: A colour channel stores the colour information for one colour component of a colour model. For example, the RGB colour model has three separate colour channels; one for red, one for green and one for blue.

ISO 19262:2015

colour constancy: high level of invariance of the visual system relative to changes in the spectral qualities of the illumination to the perception of reflective colours source – ISO 19262:2015

colour depth: here usually being the bit depth per colour channel but sometimes also used for the sum of the bit depth’s for all colour channels
Note 1 to entry: See bit depth. source – ISO 19262:2015

colour difference metric: metric based on some specified mathematical difference between the points representing a test specimen and its reference in an appropriate colour space source – ISO 19262:2015

colour distance: see colour difference

colour encoding: quantized digital encoding of a colour space, encompassing both colour space encodings and colour image encodings
source – ISO 19262:2015

colour encoding (correct): quantized digital encoding of a colour space, encompassing both colour space encodings and colour image encodings
SOURCE:ISO/TS 22028‑3:2006

colour filter array: mosaic or stripe layer of coloured transmissive filters fabricated on top of an imager in order to obtain a colour image from a single image sensor
SOURCE:ISO 12231:2005

colour fringing: existence of coloured fringes in the area of high contrast structures in images
Note 1 to entry: One of the sources for these is lateral and longitudinal chromatic aberration. source – ISO 19262:2015

colour gamut: solid in a colour space, consisting of all those colours that are either: present in a specific scene, artwork, photograph, photomechanical, or other reproduction; or capable of being created using a particular output device and/or medium.
Note 1 to entry: See also luminance ratio.
SOURCE: ISO/TS 22028-3:2006

colour image encoding: digital encoding of the colour values for a digital image, including the specification of a colour space encoding, together with any information necessary to properly interpret the colour values, such as the image state, the intended image viewing environment and the reference medium
Note 1 to entry: In some cases, the intended image viewing environment will be explicitly defined for the colour image encoding. In other cases, the intended image viewing environment may be specified on an image-by-image basis using metadata associated with the digital image.
Note 2 to entry: Some colour image encodings will indicate particular reference medium characteristics, such as a reflection print with a specified density range. In other cases, the reference medium will not be applicable, such as with a scene-referred colour image encoding, or will be specified using image metadata.
Note 3 to entry: Colour image encodings are not limited to pictorial digital images that originate from an original scene, but are also applicable to digital images with content, such as text, line art, vector graphics and other forms of original artwork.
SOURCE:ISO/TS 22028‑3:2006

colour management: communication of the associated data required for unambiguous interpretation of colour content data and application of colour data conversions, as required, to produce the intended reproductions SOURCE:ISO 15076‑1:2010

colour misregistration: colour-to-colour spatial dislocation of otherwise spatially coincident colour features of an imaged object

source – ISO 19262:2015

colour model: way of specifying or describing a colour numerically
EXAMPLE:
In the 24-bit-deep RGB colour model, the intensity of each of the red, green and blue components of the model (8 bits for each channel) are represented on a scale from 0 to 255.
Note 1 to entry: Common examples include RGB, HSV and CMYK.
Note 2 to entry: The lowest intensity of any colour is represented by 0 and the highest intensity by 255.
Note 3 to entry: There are two main categories of colour models: additive and subtractive. Additive colour models (such as RGB) are based on transmitted light while subtractive colour models (such as CMYK) are based on reflected light.

source – ISO 19262:2015

colour rendering: mapping of image data representing the colour-space coordinates of the elements of a scene to output-referred image data representing the colour-space coordinates of the elements of a reproduction
Note 1 to entry: Colour rendering generally consists of one or more of the following: compensating for differences in the input and output viewing conditions, tone scale and gamut mapping to map the scene colours onto the dynamic range and colour gamut of the reproduction, and applying preference adjustments.
SOURCE:ISO/TS 22028‑3:2006

colour re-rendering: mapping of picture-referred image data appropriate for one specified real or virtual imaging medium and viewing conditions to picture-referred image data appropriate for a different real or virtual imaging medium and/or viewing conditions
Note 1 to entry: Colour re-rendering generally consists of one or more of the following: compensating for differences in the viewing conditions, compensating for differences in the dynamic range and/or colour gamut of the imaging media, and applying preference adjustments.
[SOURCE: ISO 22028-1:2004

colour space: geometric representation of colours in space, usually of three dimensions
SOURCE:CIE Publication 17.4 (845-03-25) and ISO 22028‑1

colour space encoding: digital encoding of a colour space, including the specification of a digital encoding method, and a colour space value range
Note 1 to entry: Multiple colour space encodings can be defined based on a single colour space where the different colour space encodings have different digital encoding methods and/or colour space value ranges. (For example, 8-bit sRGB and 10 bit e-sRGB are different colour space encodings based on a particular RGB colour space.)

Note 2 to entry: This term is also defined in ISO 22028-1, ISO/TS 22028-2 and ISO/TS 22028-3.

colour space (colorimetric): colour space having an exact and simple relationship to CIE colorimetric values
Note 1 to entry: Colorimetric colour spaces include those defined by CIE (e.g. CIE XYZ, CIELAB, CIELUV, etc.), as well as colour spaces that are simple transformations of those colour spaces (e.g. additive RGB colour spaces).
SOURCE:ISO 22028‑1

colour space white point: colour stimulus to which colour space values are normalized
Note 1 to entry: It is not necessary that the colour space white point correspond to the assumed adapted white point and/or the reference medium white point for a colour image encoding.
[SOURCE:ISO 22028‑1]

colour temperature: temperature of a Planckian radiator whose radiation has the same chromaticity as that of a given stimulus

SOURCE:ISO 9241‑302

compression ratio: relationship of the file size before compression to the file size after compression
SOURCE:ISO 12651‑1:2012

continuous tone (image): image represented using a large enough number of potential tonal levels per pixel so that the differences between adjacent tonal levels are visually imperceptible in the intended use condition
Note 1 to entry: It is an image that has not undergone a graphic arts halftone screening process.
Note 2 to entry: Generally referring to pictorial images, where there is a non-broken range of tones from white to black that may have every shade of gray represented. There are theoretically an infinite number of tones. Traditional photography (photochemical photography) produces continuous tone images. When reformatting pictorial items, it is important to distinguish continuous tone originals from printed halftones, since these two classes are likely to require different strategies and methods for making the digital images.

source – ISO 19262:2015

contrast: difference between the grey levels of two specified parts of the image

SOURCE:ISO 21227‑1:2003

contrast sensitivity function (CSF): functional description of the human visual systems sensitivity to peak-to-peak luminance differences (i.e. contrast) of a range of sine wave spatial frequencies
Note 1 to entry: The CSF varies with colour and viewing conditions.
Note 2 to entry: While the CSF is dependent on the average luminance viewing conditions, a single one is usually adopted for typical conditions.

source – ISO 19262:2015

correlated colour temperature: temperature of the Planckian radiator whose perceived colour most closely resembles that of a given stimulus at the same brightness and under specified viewing conditions
SOURCE:ISO 3664:2009

colour sequential exposure: acquisition of a picture by combining repeated exposures to capture different colour components
SOURCE:ISO 12231:2012

Depth of Field: The distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image. It is influenced by aperture, focal length, and the distance to the subject.

Dynamic Range: The range of light intensities from the darkest shadows to the brightest highlights that a camera can capture in a single image. A wider dynamic range allows for more detail in both the shadows and highlights.

data rate: number of bits that are conveyed or processed per unit of time, most often (but not exclusively) employed when discussing time-based media like sound or video
Note 1 to entry: The data rate is often expressed in units of kilobits per second (kbit/s or kbps, 10 to the third power), megabits per second (Mbit/s or Mbps, 10 to the sixth power), or gigabits per second (Gbit/s or Gbps, 10 to the ninth power).
source – ISO 19262:2015

decibel (dB): one-tenth of the bel
Note 1 to entry: The decibel is more often used than the bel as a unit of level.
Note 2 to entry: The decibel can be defined as a unit of level of a power-like quantity when the base of the logarithm is the tenth root of 10. Also, the decibel is the unit of level of a field quantity when the base of the logarithm is the 20th root of 10.

SOURCE:IEC 801-22-03

decoder: equipment, application, or algorithm for decoding signals, which may include decompression of data previously compressed by an encoder
Note 1 to entry: This definition is derived from the IEC 723-07-47 definition for broadcasting, sound and television and was altered to be applicable to imaging and archiving in general.

source – ISO 19262:2015

defect: event or shortcoming that does not conform to specification
Note 1 to entry: Defects are generally classed by severity, with class one being the highest severity.

source – ISO 19262:2015

defect pixel: pixel or subpixel that operates in a way other than the one in which it is driven
[SOURCE:ISO 9241-302:2008, 3.4.30]

delta E: see colour difference

de-mosaicing: calculation of missing colors at every position of an image generated by a sensor with a colour filter array

source – ISO 19262:2015

densitometer: instrument for measuring optical densities by transmission or by reflection under standardized geometrical and spectral conditions
SOURCE:ISO 6196-6:1992

density: degree of light absorption, reflection, or scattering characteristics of a photographic image, expressed as the logarithm to the base 10 of the ratio of incident radiant flux to the transmitted, reflected, or scattered flux
SOURCE; ISO 18913:2003

depth of field: axial depth of the space on both sides of the object plane within which the object can be moved without detectable loss of sharpness in the image, while the positions of the image plane and of the objective are maintained
SOURCE:ISO 10934-1:2002

depth of focus: axial depth of the space on both sides of the image within which the image appears acceptably sharp, while the positions of the object plane and of the objective are maintained

SOURCE:ISO 10934-1:2002

device level target (DLT): test chart designed and used to test the performance and characteristics of an imaging device or an imaging system

source – ISO 19262:2015

device-dependent colour space: colour space defined by the characteristics of a real or idealized imaging device
Note 1 to entry: Device-dependent colour spaces having a simple functional relationship to CIE colorimetry can also be categorized as colorimetric colour spaces. For example, additive RGB colour spaces corresponding to real or idealized CRT displays can be treated as colorimetric colour spaces.

SOURCE:ISO 22028‑1:2004

digital code value [digital output level]: numerical value assigned to a particular output level
SOURCE:ISO 16067‑1:2003

digital file: set of related digital records held in a tightly bound relationship within the business system and managed as a single object
Note 1 to entry: At a high level of abstraction, a digital or computer file is a stored segment or block of information that is available to a computer program. Files are so named because they are the counterparts of the paper documents traditionally kept in file folders, usually stored in a file cabinet. Computer operating systems consider files as a sequence of bytes, while application software interprets the binary data as, say, text characters, image pixels, or audio samples.
SOURCE:ISO 16175‑2:2011

digital image: digital file consisting of picture elements (pixels) with one or more digital code values per pixel that represent a colour or tonal value
Note 1 to entry: A digital image can represent a natural scene or any kind of object.
source – ISO 19262:2015

digital imaging: process of creating digital images
Note 1 to entry: The term may also be used more generally to include digital image processing.

digital imaging system: system that records and/or produces images using digital data

SOURCE:ISO/TS 22028‑3:2006

digital master: raw, partially processed, or fully processed digital reference image in mostly a scene referred state that may require additional processing for output and display

source – ISO 19262:2015

digital negative (DNG): digital image file format designed by Adobe Systems

Note 1 to entry: DNG is a file format that wraps camera sensor data (“camera RAW data”) plus metadata to support image reconstruction, adjustment, and display based on the TIFF/EP (ISO 12234-2) International Standard.

digital output level: numerical value assigned to a particular output level
Note 1 to entry: This term is also defined in ISO 16067-2 and ISO 21550.
[SOURCE:ISO 14524:2009, 3.2]

digital still camera (DSC): device which incorporates an image sensor and produces a digital signal representing a still picture
Note 1 to entry: A digital still camera is typically a portable, hand-held device. The digital signal is usually recorded on a removable memory, such as a solid-state memory card or magnetic disk.

Note 2 to entry: This term is also defined in ISO 12232, ISO 15739 and ISO 17321-1.

digitization: act of generating a digital (quantized) representation of a continuous signal
SOURCE:ISO 20998-1:2006

display white point: chromaticity of a computer display’s nominal white value

SOURCE:ISO/IEC 15948:2004, 3.1.52

distortion (geometric distortion, TV distortion): displacement from the ideal shape of a subject (lying on a plane parallel to the image plane) in the recorded image
Note 1 to entry: It basically derives from variation of lateral magnification in the image field of a camera lens and results in straight lines being rendered as curves. There are other factors to induce geometric distortion, for example, rotational asymmetricity of a camera lens or position shift processing in a camera imaging process.
[SOURCE:ISO 17850]

dither: intentionally applied noise that is intended to randomize quantization error

Note 1 to entry: This can have the effect of preventing visible or audible patterns in images and sounds, such as contouring that are more objectionable than random noise. Dither is routinely used in processing of both digital audio and digital images.

Dmax/Dmin: see maximum density, minimum density
Note 1 to entry: Dmax is an abbreviation for maximum density and Dmin for minimum density.
Note 2 to entry: The abbreviations are used both in describing the characteristics of an image or an imaging device such as a scanner.

source – ISO 19262:2015

dots per inch (DPI): unit for the number of spots that a scanner (printer) can divide an image into (scan, print) per inch both horizontally or vertically
Note 1 to entry: See sampling rate.
source – ISO 19262:2015

downsampling: reduction of samples in data where the sampling rate is reduced with reference to the original sampling rate

source – ISO 19262:2015

dynamic range: difference, over a given period of time, between maximum and minimum signal levels, expressed in decibels, contrast ratios or f-stops
Note 1 to entry: The minimum signal level must be greater than a specified usable signal level.
Note 2 to entry: This definition is derived from IEC 702-04-23, but was altered to match the imaging and archiving application.

source – ISO 19262:2015

Exposure: The amount of light that reaches the camera sensor, determining how light or dark an image will appear. It is controlled by aperture, shutter speed, and ISO.

Exposure Triangle: A concept that explains the relationship between the three elements that control exposure: aperture, shutter speed, and ISO. Balancing these three factors is essential for proper exposure.

eciRGB v2: RGB colour encoding specified in ISO 22028-4

source – ISO 19262:2015

edge spread function (ESF): normalized spatial signal distribution in the linearized output of an imaging system resulting from imaging a theoretical infinitely sharp edge
Note 1 to entry: See also line spread function (3.150), point spread function (3.195).

SOURCE:ISO 16067-2:2004

effectively spectrally neutral: having spectral characteristics which result in a specific imaging system producing the same output as for a spectrally neutral object
Note 1 to entry: See also spectrally neutral.
SOURCE:ISO 16067‑2:2004

electronic scanner for photographic films: scanner incorporating an image sensor that outputs a digital signal representing a still film image

SOURCE:ISO 16067‑2:2004

electronic scanner for photographic prints: scanner incorporating an image sensor that outputs a digital signal representing a still print image
SOURCE:ISO 16067‑1:2003

electronic still-picture camera: camera incorporating an image sensor that outputs an analogue or digital signal representing a still-picture, or records an analog or digital signal representing a still picture on a removable media, such as a memory card or magnetic disk

SOURCE:ISO 12233:2000

encoder: device, application, or algorithm that encodes data, often used for data compression
Note 1 to entry: A decoder is used to play the data, which often entails decompression.

source – ISO 19262:2015

exchangeable image file format (EXIF): metadata set to accompany TIFF, JPEG, and RIFF WAV formatted image files
Note 1 to entry: Exif was prepared by the Technical Standardization Committee on AV & IT Storage Systems and Equipment and is Published by the Japan Electronics and Information Technology Industries Association (JEITA). The Exif 2.2 specification (JEITA CP-3451) is in nearly universal use by camera manufacturers. The Exif data structure is based on the TIFF tags and there is significant overlap between TIFF and Exif metadata. While, the Exif standard is almost exclusively focused on image data, it does stipulate a method of writing audio data in files. Also specified is the relational information indicating the relation between image files and audio files.

source – ISO 19262:2015

exposure (H) (photographic): total quantity of light allowed to fall upon a photosensitive emulsion or an imaging sensor (measured in lux seconds)

SOURCE:ISO 10934‑1:2002

exposure index (EI): numerical value that is inversely proportional to the exposure provided to an image sensor to obtain an image
Note 1 to entry: Images obtained from a DSC using a range of exposure index values will normally provide a range of image quality levels.
[SOURCE:ISO 12232:2006, 3.2]

exposure latitude: acceptable exposure variation without losing highlight or shadow detail
Note 1 to entry: The exposure latitude depends on the degree to which the dynamic range of the imaging system exceeds that of the scene or original to be digitized.
source – ISO 19262:2015

exposure process: various methods to capture images in the electronic still picture camera

SOURCE:ISO 12231:2005, 2.38

exposure series: series of images of the same subject taken using different exposure index values

SOURCE: ISO 12232:2006

extended gamut: colour gamut extending outside that of the standard sRGB CRT display as defined by IEC 61966-2-1
[SOURCE:ISO/TS 22028‑3:2006, 3.14]

Focal Length: The distance between the lens and the image sensor when the subject is in focus, usually measured in millimeters. It affects the field of view and magnification of the image.

fast scan direction: scan direction corresponding to the direction of the alignment of the addressable photoelements in a linear array image sensor.
[SOURCE:ISO 21550:2004, 3.7]

fiducial mark: index mark on a test system that allows automatic geometric identification and orientation detection of an object using imaging systems
source – ISO 19262:2015

file format (image): processing method to encode the image information for storage in a computer file
Note 1 to entry: Typical file formats in archiving are Tiff, JPEG, JPEG 2000, and PNG.
Note 2 to entry: Set of structural conventions that define a wrapper, formatted data, and embedded metadata, and that can be followed to represent images, audiovisual waveforms, texts, etc., in a digital object. The wrapper component on its own is often colloquially called a file format. The formatted data may consist of one or more encoded binary bitstreams, for such entities as images or waveforms, and/or textually-encoded data, often marked up with XML or HTML, for texts. The embedded metadata may be skeletal or extensive.

[SOURCE:ISO 29301:2010, 3.15]

flare: light falling on an image, in an imaging system, which does not emanate from the subject point
Note 1 to entry: See also image flare, veiling flare, veiling glare.
Note 2 to entry: Flare is also sometimes referred to as veiling glare.

source – ISO 19262:2015

flat field: area of uniform spectral radiance as measured from a specified position

source – ISO 19262:2015

focus bracketing, focus series: see focus stacking
[SOURCE:ISO 10934‑2:2007, 2.28.2]

focus stacking: image stack acquired at different focal positions
[SOURCE:ISO 10934‑2:2007, 2.28.2]
Note 1 to entry: A digital imaging process that combines multiple images focused on different distances at parallel planes on a three-dimensional object to produce an image with a greater depth of field than could be achieved with a single image. The technique is most commonly used in macro photography and photo microscopy.

gain: quantitative expression of a power increase by the ratio of the values at two points of a power or of a quantity related to power in a well defined manner
Note 1 to entry: By extension, the word “gain” may represent the ratio of powers in a given situation and in a reference condition; for example, the “gain of an antenna”.
Note 2 to entry: Gain is generally expressed in logarithmic units by a positive or negative value. When a gain has a negative value in logarithmic units, attenuation may be used instead of gain.
[SOURCE:IEC 702-02-11]

gain modulation: variation of the gain over the signal level.
Note 1 to entry: One example for a gain modulation is the application of a gamma to an image.

source – ISO 19262:2015

gamma: exponent that describes approximations to certain non-linear transfer functions encountered in image capture and reproduction
Note 1 to entry: Within this International Standard, gamma is the exponent in the transfer function from display_output to image_sample. Image_sample = display_output gamma where both display_output and image_sample are scaled to the range 0 to 1.

[SOURCE:ISO/IEC 15948:2004, 3.1.20]

gamma correction: process that alters the image data in order to modify the tone reproduction
Note 1 to entry: Gamma correction is performed in part to correct for the nonlinear light-output versus signal input characteristic of the display. The relationship between the light input level and the output signal level, called the OECF, provides the gamma correction curve shape for an image capture device.
Note 2 to entry: The gamma correction is usually an algorithm, lookup table, or circuit which operates separately on each colour component of an image.
Note 3 to entry: This term is also defined in ISO 12233, ISO 16067-1, ISO 16067-2 and ISO 21550.

gamut, colour: see colour gamut

gamut mapping: mapping of the colour-space coordinates of the elements of a source image to colour-space coordinates of the elements of a reproduction to compensate for differences in the source and output medium colour gamut capability
Note 1 to entry: The term “gamut mapping” is somewhat more restrictive than the term “colour rendering” because gamut mapping is performed on colorimetry that has already been adjusted to compensate for viewing condition differences and viewer preferences, although these processing operations are frequently combined in reproduction and preferred reproduction models.

SOURCE: ISO/TS 22028-2:2006, 3.14

gray card: test chart consisting of a spectrally neutral or effectively spectrally neutral single test pattern at a defined reflectance or transmittance value in a prescribed spatial arrangement

source – ISO 19262:2015

gray scale (grey scale pattern): test chart consisting of test pattern based on spectrally neutral or effectively spectrally neutral, and consists of a large number of different reflectance or transmittance values in a prescribed spatial arrangement
Note 1 to entry: Grey scale patterns are typically used to measure opto-electronic conversion functions.
Note 2 to entry: This term is also defined in ISO 16067-1, ISO 16067-2 and ISO 21550.

[SOURCE:ISO 12233:2000, 3.32.2]

Histogram: A graphical representation of the tonal values of an image, showing the distribution of shadows, midtones, and highlights. It helps photographers assess exposure and contrast.

hardcopy: representation of an image on a substrate which is self-sustaining and reasonably permanent
EXAMPLE: Prints, transparencies.
Note 1 to entry: See also softcopy

SOURCE:ISO 3664:2009

horizontal resolution: resolution value measured in the longer image dimension, corresponding to the horizontal direction for a “landscape” image orientation, typically, using a vertically oriented test-chart feature
[SOURCE:ISO 12233:2000, 3.9]

high dynamic range imaging (HDR): set of techniques that allow a greater dynamic range of exposures or values (i.e. a wide range of values between light and dark areas) than normal digital imaging techniques
Note 1 to entry: The intention is to accurately represent the wide range of intensity levels found in such examples as exterior scenes that include light-colored items struck by direct sunlight and areas of deep shadow.

source – ISO 19262:2015

HSV: abbreviation for the hue, saturation and value colour model
SOURCE:ISO/IEC 9592‑1:1997

hue: attribute of a visual sensation by which the colour of a specimen is judged to be similar to one of the perceived colours, red, yellow, green or blue, or to a combination of two of them

SOURCE:ISO 105‑A08:2001, 2.15

hyperbolic wedge: bar target resolution feature where spatial frequencies increase linearly (i.e. hyperbolic) with distance making a wedge or fluted appearance to the feature
Note 1 to entry: Its utility lies in the extended high frequency portions of the target.
source – ISO 19262:2015

ISO: A measure of the camera sensor’s sensitivity to light. Higher ISO values allow for shooting in lower light but can introduce noise or grain into the image.

image aspect ratio: ratio of the image width to the image height SOURCE: ISO 15740:2008

image compression: process that alters the way digital image data is encoded in order to reduce the size of an image file
SOURCE:ISO 12233:2000

ISO DSC dynamic range: ratio of the maximum exposure level that provides a pixel value below the highlight clipping value to the minimum exposure level that can be captured with an incremental signal-to-temporal-noise ratio of at least 1, as determined in accordance with ISO 15739
[SOURCE:ISO 12231:2012, 3.86]

ISO scanner dynamic range: difference of the maximum density where the incremental gain is higher than 0,5, as determined according to ISO 21550 to the minimum density that appears unclipped
SOURCE:ISO 21550:2004

image flare: unwanted increase in signal resulting from light incident on an image sensor that does not emanate from the subject point
Note 1 to entry: While image flare can result from a variety of causes, the following four are common: internal multiple reflections between lens surfaces, light diffusion at lens barrel, body, or edge of lens, leaking of light, and the tails of the lens optical transfer function including spherical and comatic aberrations. Differentiation between these four may be difficult once an image is captured, but it is more appropriate to evaluate the last one with regard to the system resolution. Thus, care should be taken to minimize optical transfer function contribution in the measurement of image flare.
Note 2 to entry: “Image flare” was defined in ISO 3664:2000 in another context but it was deleted in ISO 3664:2009.

International Colour Consortium (ICC): consortium established in 1993 to create, promote and encourage the standardization and evolution of an open, vendor-neutral, cross-platform colour management system architecture
Note 1 to entry: The resulting ICC specification (ISO 15076-1:2005) provides a cross-platform format to translate colour data between devices in order to ensure colour fidelity, and is specified in many International Standards.

source – ISO 19262:2015

Leading Lines: A compositional technique that uses natural lines within the scene to direct the viewer’s eye toward the main subject of the photograph.

Lens Distortion: An optical aberration that causes straight lines to appear curved in an image. Common types include barrel distortion (lines bow out) and pincushion distortion (lines bow in).

Lens Flare: A phenomenon where light is scattered or flared in a lens system, often producing bright spots or streaks in an image, usually caused by strong light sources like the sun.

lossless compression: data file compression technique where the decompressed image is identical to the original uncompressed image
SOURCE:ISO 12651:1999

lossy compression: data file compression technique where the decompressed image may not be identical to the original uncompressed image
SOURCE:ISO 12651:1999

Macro Photography: A type of photography that involves capturing close-up images of small subjects, often using a macro lens, to reveal intricate details that are not visible to the naked eye.

Metering: The process by which a camera measures the brightness of a scene to determine the appropriate exposure. Common metering modes include spot, center-weighted, and matrix.

Noise: Unwanted grainy texture or color distortion in a photograph, usually more noticeable at higher ISO settings or in low-light conditions.

Panning: A technique used to capture moving subjects by moving the camera along with the subject’s motion. This results in a sharp subject with a blurred background, conveying a sense of speed.

Post-Processing: The process of editing and enhancing a photograph after it has been taken, using software such as Adobe Photoshop or Lightroom. This can include adjustments to exposure, color correction, cropping, and retouching.

Prime Lens: A lens with a fixed focal length, such as 50mm, as opposed to a zoom lens. Prime lenses typically offer superior image quality and larger apertures.

pixel aspect ratio: ratio of the distance between sampling points in the two orthogonal sampling directions
Note 1 to entry: If the distances are equal, the pixel aspect ratio equals 1:1, and is said to be “square”.
Note 2 to entry: See also image aspect ratio SOURCE:ISO 12231:2005

RAW: A file format that captures all image data recorded by the sensor, offering greater flexibility in post-processing compared to compressed formats like JPEG.

Rule of Thirds: A composition guideline that suggests dividing the frame into a 3×3 grid and placing the subject along the lines or at their intersections to create a more balanced and engaging image.

Shutter Speed: The amount of time the camera’s shutter remains open to allow light to hit the sensor. It is measured in seconds or fractions of a second and affects motion blur and exposure.

sampling aspect ratio: ratio of the sample spacing in the two orthogonal sampling directions
SOURCE:ISO 12231:2012

single exposure: acquisition of a picture by a single exposure, with one or more image sensors, that exposes all sensor pixels, all colours, and all image locations at the same time
SOURCE:ISO 12231:2012

Telephoto Lens: A lens with a long focal length that magnifies distant subjects, making them appear closer. Telephoto lenses are commonly used in wildlife, sports, and portrait photography.

Time-Lapse: A photographic technique that involves taking a series of photos at set intervals to create a video that shows changes occurring over time, often used to capture processes like sunsets or blooming flowers.

time sequential exposure: acquisition of a picture by combining repeated exposures to capture different spatial components
[SOURCE:ISO 12231:2012, 3.52.3]

Note 1 to entry: Time sequential exposure can be with a line array (line scanning) or an area array. With a line array, the picture is acquired by optical or physical sub-scanning with an image sensor in one dimension. With an area array, repeated exposures may integrate smaller pictures into a larger picture by means of image sensor shifting.

Viewfinder: The component of the camera through which the photographer looks to compose and focus the image. It can be optical (OVF) or electronic (EVF).

Vignetting: A reduction in image brightness or saturation at the edges compared to the center, often used intentionally to draw attention to the center of the frame, but it can also be an undesirable lens effect.

visually lossless compression: form or manner of lossy compression where the data that is lost after the file is compressed and decompressed is not detectable to the eye; the compressed data appearing identical to the uncompressed data
Note 1 to entry: Visually lossless compression according to this definition is independent of the viewing condition meaning that even at highest magnification levels the difference to uncompressed data is visually imperceptible.

source – ISO 19262:2015

White Balance: A camera setting that adjusts the colors to match the actual lighting conditions, ensuring that whites appear white and colors are accurately represented.

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