Microtek ScanMaker IIG User Manual page 257

Dynamic range
The ability of a scanner to register a wide range of tonal values —
something from near white to near black. A scanner with good dynamic
range is able to map input shades correctly to output shades, making
images look brighter and with more visible detail. Generally, the number
of bits determines the maximum dynamic range of a scanner. For example,
a 36-bit scanner has a higher dynamic range than a 24-bit scanner.
Exposure
The amount of light in an image. The exposure of an image can be
changed by increasing or reducing available light.
File format
The way a graphic file is saved. Several file formats are available for use,
and each one has its own advantages and disadvantages. The most popular
file formats include TIFF, PICT, EPS, and PCX. TIFF is the most widely
used file format.
Filters
Tools that allow you to apply or create special effects to your images.
Filters in your scanning software include Blur/Blur More, Sharpen/
Sharpen More, Emboss, and Enhance Edges.
Gamma
The contrast affecting the mid-level grays or midtones of an image.
Adjusting the gamma of an image allows you to change brightness values
of the middle range of gray tones without dramatically altering the
shadows and highlights.
Grayscale
An image type that contains more than just black and white, and includes
actual shades of gray. In a grayscale image, each pixel has more bits of
information encoded in it, allowing more shades to be recorded and
shown. 4 bits are needed to reproduce up to 16 levels of gray, and 8 bits
can reproduce a photo-realistic 256 shades of gray.
Halftone
A type of single-bit image composed of a pattern of black dots that fool
the eye into seeing shades of gray. Examples of halftone images are the
pictures you see in a newspaper. These images usually look very coarse.
Highlights
The lightest portions of an image.
Appendix J: Glossary J-3