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Glossary: S

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Sample (signal)
The measured value of a signal at a single point in time or space.…
Sampling frequency (signal)
The frequency that a signal is sampled along an axis of time or space.…
See Also Sampling rate (audio); Sampling rate (image)
Sampling rate (audio)
Sampling rate or sampling frequency defines the number of samples per second (or per other unit) taken from a continuous signal to make a discrete or digital signal. For time-domain signals like the waveforms for sound (and other audio-visual content types), frequencies are measured in in hertz (Hz) or cycles per second. The Nyquist–Shannon sampling…
Sampling rate (image)
The spatial frequency of the digital sampling. The reciprocal of the center-to-center distance between adjacent pixels.…
Saturation
The attribute of color that expresses the degree of departure from a gray of the same lightness. When a color has no saturation, it is a shade of gray. Saturation describes the purity of a color, and along with hue and brightness is among the three attributes that specify a color.…
Scene-referred
See Image state
Scotopic sensitivity
Scotopic sensitivity refers to visual sensitivity under conditions of low light, where radiant energy stimulates the rods (retinal photo-receptors that are achromatic, containing only one type of pigment). Scotopic vision does not involve the perception of color.…
See Also Photopic sensitivity; Mesopic sensitivity
Sensitivity
The reciprocal of the amount of light necessary to achieve a desired output response.…
Sensor array
See Array
Service file
See Derivative file
SFR
Spatial Frequency Response (SFR) describes an imaging system\'s ability to maintain the relative contrast of input stimuli.…
See Modulation transfer function
Sharpening
Amplification of the SFR by means of image processing to achieve sharper appearing images. Also, a class of image processing operations that enhances the contrast of selective spatial frequencies, usually visually important ones.…
Sharpness
The visually perceived quality of being crisp or of containing detail.…
Sheetfed scanner
A sheetfed scanner (also referred to as an automatic document scanner or ADF scanner) is a digital imaging system specifically designed for scanning loose sheets of paper, widely used by businesses to scan office documents and less frequently used by archives and libraries to scan books that have been disbound or other robust unbound documents.…
See Also Automatic document feeder; Duplex scanner
Sidecar file
See XMP sidecar file
Sidecar metadata
See XMP sidecar file
Signal-to-noise ratio
Abbreviated as SNR, it is a measure of the relative power of a desired or ideal signal to the power of an undesired signal or noise. SNR is typically measured in decibels.…
See Also Decibel; Peak signal-to-noise ratio
Skew
The angle of deviation in a digital image from the paper edge, text lines or other visual reference elements. Skew is expressed numerically as the tangent of the deviation angle in degrees, either clockwise or counterclockwise. It applies to the angle of two-dimensional image orientation. Skew is a common occurance in automatic…
Slant edge target
An imaging performance target used to measure the SFR and resolution of an image capture device using edge gradient analysis.…
SNR
See Signal-to-noise ratio
Sound field
Indicates the aural space arrangement of a mono, stereo, or multichannel sound recording, e.g., monaural, stereo, joint stereo, surround sound 5.1, etc. The term generally is used in a playback context, where a set of loudspeakers have been set up, e.g., for a surround sound presentation in a theater. The term may be compared to…
See Also Multichannel (audio); Channel (audio); Track (audio)
Source metadata
See Metadata source
Spatial frequency
The reciprocal of the distance between any two cyclical spatial features.…
Spatial frequency response
See SFR
Spatial resolution
See Resolution
SPC
See Statistical Process Control
SPD
See Spectral Power Distribution
Spectral Power Distribution
Spectral Power Distribution (SPD) curves chart the spectral characteristics of a light source, showing the radiant power of the light source at each wavelength or band of wavelengths across the visible spectrum.…
Spectrodensitometer
A densitometer that makes use of spectral data, providing densitometric readings at discrete spectral intervals.…
See Densitometer
Spectroradiometer
A spectroradiometer is an instrument designed to measure the spectral power distributions of illuminants, measuring the radiant power from a light source as a function of wavelength.…
Specular reflection
See Reflection specular
sRGB
Standard RGB color space created by HP and Microsoft for use on monitors, printers, and the Internet. sRGB uses the ITU-R BT.709-5 primaries that are also used in studio monitors and HDTV, and a transfer function (gamma correction) typical of CRTs, all of which permits sRGB to be directly displayed on typical monitors. The sRGB…
See Also Color model; Gamma correction
Stacking
See Focus Stacking
Standard illuminant
A standard illuminant is a published spectral profile of visible light. The most commonly used and referred to standard illuminants are published by the CIE. A CIE illuminant is a spectral characterization or model that defines the amount of energy at each wavelength across the spectrum. Physical light sources listed as…
See CIE
Statistical Process Control
Statistical Process Control (SPC) is a method of monitoring and controlling processes through statistical analysis. The basic components of SPC include measuring and monitoring the processes, eliminating variances to maximize consistency, and improving the process to meet or exceed requirements or specifications. Control charts are a common tool in SPC and are used to…
Stitching
An image processing method combining multiple overlapping images to create a single image. Stitching can be used in scanning where a single scan of a large object is not able to produce sufficiently high resolution. Accurate digital alignment to create a visually seamless and uniform image from the individual component images is technically complex and…
Structural metadata
See Metadata structural
Structured audio
Dynamically constructed sound resulting from the processing of data through combinations of software and hardware. Such software includes sequencers and trackers that use data to control when individual sound elements should start and stop, to set values for attributes such as volume and pitch, and for other effects that should be applied to the…
See Waveform (sound)