alien  Scanners  alien


CCD
Charge Coupled Device which is a semiconductor technology used by light-sensitive electronic devices, including scanners and digital cameras.
Color Calibration
The capability of changing the levels of color (red, green, and blue in scans).
Color Channels
Digital representations of the three components of white light: red, green, and blue light. Each channel can be manipulated independently of the others.
Densitometer
An instrument used to measure the shadows, midtones, and highlight values of images to be reproduced on a computer.
Descreening
A feature designed to preserve the look of previously printed images such as photographs from a magazine.
DPI
Dots per Inch
Gamma
A numerical representation of contrast that lets you enhance midtones and shadow detail without washing out highlights.
Gray scale
The graduation from white to black in an image. Generally, an 8-bit scan would be composed of 256 shades of gray.
Historgram
With scanners, a chart that shows the distribution of light and dark pixels. By identifying this distribution, you can plan an effective strategy for your necessary tonal adjustments.
Interpolated Resolution
This feature can rectify the "jaggies" on black and white line art but can result in a loss of precision and sharpness in continuous tone (for example, a photograph) images. Compare with optical resolution.
LPI
Lines per inch, the higher the LPI, the finer the image.
Optical Resolution
The true resolution of a scanner is determined by the number of CCD elements in its scan mechanism. Essentially, the more CCD elements, the higher the resolution. Compare with Interpolated Resolution.
Pass, Single vs Triple
Most desktop color flatbed scanners read image information with a single pass of their read head. Others scan three separate times: one pass for each color (red, green, and blue) composing the reflected white light. In theory, triple-pass scans provide better color, whereas single pass scanners are faster.
PPI
Pixels per Inch, the higher the PPI, the better the scan.
Sample Bit Depth, Ext.
The bit depth at which an image is scanned by the scanner itself. The higher the bit count, the better the scan.
Sharpening Filter
Sharpening intensifies the differences in light and dark passages in an image. It provides a good approach to adding snap to gray-scale images before converting them to line art, but oversharpening can also draw unwanted attention to elements - such as scanning artifacts - that you would not want to enhance.
TWAIN
Technology Without an Interesting Name. Any application that conforms to this standard can access a TWAIN - compliant scanner.

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Date of Last Revision: 21 December 2001
Extracted from the InfoWorld Magazine, January 1996