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Glossary: H

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H and D Curve
The tone scale of a photographic negative is non-linear, with a relatively linear mid-section and lower contrast at both the high and low density parts of the film image. If measured and graphed, the values would look somewhat like the letter S. This is known as the H and D Curve. Alternate spellings include H&D…
Handprint Character Recognition (HCR)
Handprint character recognition (HCR) is a process that converts handwriting or lettering into machine generated characters. It is related to OCR, which converts dots or pixels representing machine generated characters in a raster image to be converted into digitally coded text. This is also known as Intelligent Character Recognition (ICR). Because of the highly variable…
See Also OCR; ICR
Hash algorithm
A hash algorithm is a function that converts a data string into a numeric string output of fixed length. The output string is generally much smaller than the original data. Hash algorithms are designed to be collision-resistant, meaning that there is a very low probability that the same string would be created for…
See MD5 (checksum)
HDR imaging
See High dynamic range imaging
Header Tags
See TIFF header tag
High dynamic range imaging
In photography and computer graphics, high dynamic range (HDR) imaging is a 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. The intention is to accurately represent the wide range of intensity levels found in…
See Also Bit depth (image); Dynamic range
A color model based on hue (H), saturation (S) and luminous intensity (V), the amount of light emitted by a particular color (described by H & S).…
See Color model
The attribute of color described by words such as red, blue and yellow. Hue, along with saturation and brightness are the three attributes that specify a color.…
Hyperbolic wedge
A bar target resolution feature where spatial frequencies increase linearly ( i.e. hyperbolic) with distance making a wedge or fluted appearance to the feature. Its utility lies in the extended high frequency portions of the target.…