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Glossary of Scanning Terms

 

AdaptiveThresholding
 Advanced 2-D Adaptive Thresholding estimates the background gray level in a window area around each pixel. The difference between the actual pixel value and the background is then compared to the adaptive settings to determine if a pixel is thresholded as a black or a white pixel.
Additive Colors:
 The additive primary colors are red, green and blue. These additive primaries represent the three main components of white light. Used individually or together, these three colors of light can be mixed to create nearly all colors. When these three primary colors are mixed in equal parts they produce white. Additive color is used in scanners and computer displays.
ADL+ Error Diffusion Halftoning
 Image Processing that supports visibility of graytones in printed output by adding toned shades of gray in regions between black and white. Carried out as a segment of Dual 2D-Adaptive enhancement processing in copy modes.
ALE - Accuracy Lens Enhancement
Accuracy Lens Enhancement (ALE) is an electronic correction of spherical errors in CCD based camera- scanning systems.
When looking at pixels across the range of a camera, the pixels tend to be more elliptical at the outside edges of the lens and more round in the middle of the lens. This anomaly is known as a spherical lens error and can introduce inaccuracies in the scanning system that can vary quite substantially between different points along the scan line.
Most manufactures typically state a +-0.1% accuracy of the scanner between the two outermost end-points of the scan line. However, when measuring between two points that do not fall across the entire scan line, it is not unusual to see variations of up to +- 0.5% or even higher. This is naturally unacceptable in demanding environments and markets such as GIS, which need a stable and well-defined maximum error of 0.1% or less.
ALE solves this problem by a process to electronically correct the spherical errors in the scanner and maintain a stable maximum error across any two points of less than 0.05% ± 1 pixel.
ATAC Automatic Thickness Adjustment Control - A special technology that allows the scanner pressure platen to be raised to accommodate thick originals and then lowered - both actions performed by pressing a key from the operators panel. Sensors in the platen detect when perfect pressure is applied to the the original and automatically stop the downwards motion of the platen so it rests on the original with an optimal grip.
 
Bitmap:
 An image format made from a matrix of individual pixels. .bmp.
Bitmapped Image:
 A bitmapped image is a computer file representing a line-art image that was scanned with a scanner. Refers to the pattern (map) of bits that are either black or white.
Black Level:
 The Black Level is a setting in scan programs used to change dark graytone colors to true black. For example, if one is copying a brochure with a mixture of text and pictures, the text will often be digitized to a color that we may see as black but really is a dark graytone. When the printer digests this graytone data, it will print the original's text with a halftone pattern, meaning scattered dots instead of solid black. By increasing the Black Level value, one can get the text to be copied in real black and it will therefore appear clearer.
Black Point Adjustment:
 An adjustment made that will determine the amount of shadow detail in an image. It is considered proper to set the black point so that the darkest part of an image will only just have zero detail.
Blueprint:
 A process of photographic printing used mainly for copying architectural and mechanical drawings;  produces blue lines on a white/bluish background.
Blur:
 The averaging of pixel elements.
Brightness Adjustment:
 An adjustment on a scanner that allows the user to compensate for a light or dark original.
 
Calibration:
 Adjusting a device so that it performs in accordance with an established standard. Scanner calibration is minimizing color deviation between scanned ANSI IT8 reference color patches and the known color reference values. Generally, Calibration is the process of setting a device to known color conditions - stabilizing the device to a known and quantifiable state. Calibration is commonly done with devices that change color frequently, such as monitors (phosphors lose brightness over time), scanners (light changes)  and printers (proofers and other digital printing devices can change output when colorant or paper stock is changed).
CALS:
 Computer-aided Acquisition and Logistics Support (CALS) standard, a U.S. Defense Department and industry initiative that addresses the design, manufacture, and support issues of generation, access, management, and use of technical data in digital form.
CCD:
 Charge Coupled Device, CCD is the image sensor in the scanner that converts light to voltages. These voltages are converted by the scanner into the image.
CCITT Group3:
 Standard runlength compression format used with FAX transmission. It utilizes modified Huffman coding to further compress the runlength numbers. Most scanner file formats are dialects of this format.
CCITT Group4:
 Two-dimensional compression format, giving very compact image files. Standardized by CALS (MIL 28002) and ISO-ODA for Drawing Archival and Interchange.
CIE LAB:
 A device-independent color space specified by CIE, used in modern color management software to facilitate conversion of data from a scanner to a display, or from a display to an output device.
CIE:
 Centre Internationale d'Eclairage (CIE) is an international organization that establishes methods for measuring color. These color standards for colormetric measurements are internationally accepted specifications that define color values mathematically. The first color space model, the CIE xyz, was developed in 1931. CIE defines color as a combination of three axes: x, y,and z. The two color spaces released in 1978 are CIE Lab and CIE Luv. The goal was to provide an accurate and uniform reference of visual perception.
CMYK:
 The subtractive printing colors. Cyan, Magenta, Yellow, Black.
Color Balance:
 The visual effect of an image when the amount of each color and the overall amount of color are balanced.
Color bit depth:
 The simplest pixel has two options: black or white. (A pixel with two choices is known as a 1-bit image, or two raised to the power of one). Adding more bit information increases the number of color options. The number of potential color options for a pixel is called color bit depth. For example a 4-bit pixel would have 16 color options, and an 8-bit pixel would have 256 color options, while a 24-bit pixel would have 16,777,216 color options.
Color Cast:
 An image is said to have a color cast if its colors are not true. A color cast will usually be described by stating the particular color predominant in the image, e.g., the grass appears to have a red color cast.
Color Correction:
 To improve the color rendition. Correcting for, and eliminating an unwanted color cast.
Color Management System:
 Color Management System (CMS) software increases the accuracy of color interchange between scanners, displays and printers based on profiles for each device. The CMS is a layer of software resident on the computer that negotiates color reproduction between the application and color devices. The CMS performs the color transformations necessary to exchange accurate color  between diverse devices. The Color manager needs access to characterization data for the device. The format and content of such device profiles is standardized by the International Color Consortium (ICC.)
Color Separation:
 Process of separating colors, in an image, into primary color components for printing. Converting an RGB color image into CMYK color image. Color separation is a technical function during which critical settings such as GCR, black ink limit and total ink limit are applied to the image.
Color Space:
 A color space is a particular language used to describe color. Examples of color spaces are: RGB, CMYK, HSV, CIE LAB.
Contrast:
 The difference between the lightest and darkest significant areas in a picture. A picture with high contrast has nearly white areas and nearly black areas with sharp changes in brightness between them. The picture seems dominated by stark light and dark tones.
 
Density units:
 Photographers and printers measure transmission in base-10 logarithmic density units, where transmission of unity corresponds to a density of 0, transmission of 0.1 corresponds to a density of 1, transmission of 0.01 corresponds to a density of 2, and so on
Density:
 The light stopping ability of a film. Density is inversely proportional to the amount of light reflected or transmitted by an image.
Device Dependent Color Space:
 For example RGB. A device dependent color space, e.g., the same scan file will appear different when viewed on different computer displays.
  For example CIE LAB. A device independent color space is one in which color values are absolute, e.g., defined by CIE standard. CIE LAB is the central color space in color management systems (CMS) and is used to translate between different device dependent color spaces such as scanner RGB and display RGB.
Device Profile:
 A file used as part of a Color Management System (CMS). A device profile contains information about the characteristics of a scanner, computer display or printer. The format for device profiles (Win95, Colorsync. etc.) is standardized by ICC (International Color Consortium).
DIP
 Digital Image Processor. Hardware embedded function that does image enhancement in real-time while scanning.
Dither:
 To use patterns of different colored pixels to create blended colors; or, to use dots of different sizes to simulate grayscale images. (see below)
Dithering:
 A printing or display device may have only a small number of  grayscale or color values for each device pixel. However, if the viewer is sufficiently distant from the printed page or display, the value of neighboring pixels can be set so that the viewer's eye integrates several pixels to achieve an apparent improvement in the number of levels or colors that can be reproduced.
Dots Per Inch (dpi):
 A measure of dots in a square inch where the individual element is a round dot on the printed page.
DPI:
 Dots Per Inch, equivalent to Pixels Per Inch. An expression of resolution of a scanned image.
Drag:
 Press the left mouse button and move the mouse while keeping the button pressed. When the desired action is completed, release the mouse button. Drag refers to an action sequence (mouse down, mouse move, mouse up), such as "Drag the button in the scroll bar. . ."
DSP:
 Digital Signal Processor, does image enhancement in real-time while scanning.
Dual 2D-Adaptive Enhancement
 Enhancement processing on the foreground and background separately. Processing is performed on-the-fly. The separate enhancement processes are simultaneously performed on different drawing aspects.
Dynamic Range:
 A measurement of scanner quality; the density difference between highlights and shadows.
 
Edit:
 Modify an entry using standard Windows text-editing techniques.
Emulsion:
 The light sensitive silver, coated on the clear acetate film base, that forms the photograph when a picture is taken and the film is developed.
Equalizing:
 Distributing all color or tone equally along a density range.
 
File Format (image):
 The format in which a scanned picture is saved. Many programs can insert or import a picture from a file, if it is saved in a file format that the program supports. Common file formats include TIFF (Tagged Image File Format), BMP (Windows bitmap), JPEG (Joint Photograph Expert Group), and FPX (FlashPix format).
Flip Horizontal:
 To flip the picture left/right.
Foreground:
 Foreground when scanning raster data (black and white, or monochrome data) refers to the pixels that represent data of interest (background refers to everything else). Typically, lines and shapes are represented by black pixels (foreground) and empty space is represented by white pixels (background). When scanning grayscale data, background means the gray level of a region of pixels that surrounds some desired foreground data.
 
Gamma Adjustment:
 An adjustment that makes the tone distribution lighter or darker in an image.
Gamut Transformation:
 Color Management System function, where out-of-gamut colors are converted to colors within the gamut of the targeted device, e.g., a printer.
Gamut:
The color range scanable, printable or displayable by a device; e.g., if some of the displayable colors are outside of the gamut of the printer they cannot be printed.
GCR:
Gray component replacement. A color separation setting used on color photographs where cyan, magenta and yellow inks are replaced by black ink (in a balan