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Glossary: R

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Radiometric
Of, or pertaining to, the measurement of radiant energy. It often implies the absolute measured radiant energy of incremented wavelengths not necessarily constrained to the visible portion of the spectrum.…
Radiometric distortion
See Also Distortion; Radiometric
Radiometry
Radiometry is the science involved with the measurements of electromagnetic radiation in the visible, ultraviolet and infrared spectral regions. As opposed to photometry, radiometry is does not factor the response function of the human eye. …
Raster data
Data in which a grid or raster of picture elements (pixels) has been mapped to represent a visual subject, e.g., the page of a book or a photograph. The term is derived from the Latin word for rake, suggesting the way in which that tool can be used to inscribe a grid pattern. The…
See Also Raster image; Vector data
Raster image
Image based in raster data.…
Raster Image Processor
See RIP
RDF
Resource Description Framework (RDF) is a W3C specification for a metadata data model in the form of subject-predicate-object expressions. This RDF triple has been extended from its original use to describe resources available on the Internet to become an information modeling tool that underlies the W3C's Semantic Web. An important aspect to RDF is…
Reflection densitometer
See Densitometer
Reflection, diffuse
Diffuse reflection occurs when light is reflected off a rough surface, scattering the rays of light in a broad range of directions. The higher the degree of scattering of the reflected light relative to the incident light, the more diffuse the reflection. Flat house paint (rough and irregular when magnified) is generally used on…
See Reflection, specular
Reflection, specular
Specular reflection is the type of reflection observed when light is reflected off a shiny, glossy or mirror-like surface, where light from a single incoming direction is reflected into a single outgoing direction. Stated in more standard terminology, the angle of incidence of the light ray is equal to the angle of reflection. Specular…
See Reflection, diffuse
Reflective object
An object that is intended to be, or is generally, viewed or used in a manner in which some or all of the of light that strikes its surface is reflected. Most reflective objects are largely opaque, but may be translucent. For example, thin printed paper transmits a significant portion of the light striking…
Reflective scanning
Digital imaging of an object where light is reflected from the object, generally a reflective object such as a map or printed page of text.…
Rendering intent
Method or set of instructions for mapping or translating color values from one color space to another, generally when converting from a color space with a larger gamut to one with a smaller gamut. ICC defines four rendering intents (absolute colorimetric, relative colorimetric, perceptual and saturation).…
Representation (PREMIS term)
The set of files, including structural metadata, needed for a complete and reasonable rendition of an Intellectual Entity. For example, a journal article may be complete in one PDF file; this single file constitutes the representation. Another journal article may consist of one SGML file and two image files; these three files constitute the representation. A…
See Also Digital package; Intellectual entity (PREMIS term)
Resolution
An imaging system’s ability to resolve finely spaced detail. The level of spatial detail that can resolved in an image. The maximum spatial frequency of any utility for an imaging system (limiting resolution). …
Resolving power
See Resolution
Resource Description Framework
See RDF
RGB
An additive color model based on the three primary colors of red (R), blue (B) and green (G).…
Rights metadata
See Metadata, rights
RIP
A raster image processor (RIP) is a hardware or software application that translates page description commands into bitmapped information for an output device such as a printer.…
RMS Noise
See Noise
ROI
Region of Interest (ROI) - Any contiguous area portion of an image selected for processing, measurement, or interrogation.…