Instructs the scanner to scan the original within the single scan area with Grayscale composition. Grayscale composition uses 4 bits per pixel to represent 16 different shades of gray. At a resolution of 300 dots per inch, a grayscale scan records 1200 bits of information per inch for each horizontal inch scanned, or 360,000 bits per square inch.
Grayscale composition can be used for only one scan area. No other scan areas can be present. The scan area designated as Grayscale composition is indicated in the Scanner window by a wide dark dotted line.
When creating a Grayscale composition scan area, AppleScan enables the Contrast & Brightness settings. Choose Contrast and Brightness to set the contrast and brightness levels.
When a window contains a grayscale image, the window title in the View menu displays a Grayscale icon.
A grayscale image can be displayed on any monitor that can display 16 shades of gray, such as a color monitor or a high-resolution monitor. The correct monitor setting for the Macintosh II with an extended video card is 8-bits grayscale, 256 levels. You change this setting in the Control Panel.
If the monitor being used cannot display 16 shades of gray, AppleScan displays the image in black and white. Displaying the image as Line Art composition does not effect the grayscale information in memory or in a saved document.
Grayscale images can be converted to halftone or line art by using the Converter. A conversion can be performed immediately, or save the grayscale image and convert it at a later time.
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Halftone
This setting selectes the pattern to be used when scanning in the halftone mode. The setting effects Halftone composition scans and conversions of grayscale images to halftone. The halftone pattern is a 4—by—4 dither matrix that determines the manner in which shades of gray are presented in the scanned image.
Use the Locator tool to display a representative area of the image to use with the Halftone Pattern setting. You can see and print this area using different halftone patterns. Refer to the Setting dialog box.
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Line Art
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Preview
Instructs the scanner to perform a 75 dots per inch (dpi) resolution, 100% scale, in Line Art composition.
A preview is effected by the Threshold setting and the Graymap setting. Typically, Preview is used to obtain a rough scan image to set scan areas prior to using Scan.
A preview scans the entire scanner glass, ignoring any scan areas set in the Scanner window.
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NOTE: The Scan Control Panel provides access to the same controls and instructions as the Scan menu. You can operate the scanner by using either the Scan Control Panel or the Scan menu, depending on you preference.
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You can use one of three compositions — Line Art, Halftone, or Grayscale. A line art composition scan records only black and white from the original. A halftone composition scan records gray shades on the original, using a pattern of black and white dots to represent these shades.
