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Note: The scanner uses either the selected Color/Grayscale option or the selected Monochrome option. Which one is used
depends on the settings you select in the Acrobat Scan dialog box or in the scanner's TWAIN interface, which may open
after you click Scan in the Acrobat Scan dialog box. (By default, the scanner application dialog box does not open.)
When scanning black-and-white or monotone images, select one of the following:
Monochrome
•
Applies the JBIG2 compression method to black-and-white input pages. Settings of 0.95 or higher use the
JBIG2
lossless method; at lower settings, text is highly compressed. Text pages typically are 60% smaller than CCITT Group
4 compressed pages, but processing is slow. Compatible with Acrobat 5.0 (PDF 1.4) and later.
Note: For compatibility with Acrobat 4.0, use a compression method other than JBIG2.
•
(As described above, under Color/Grayscale settings.)
Adaptive
•
Applies CCITT Group 4 compression to black-and-white input page images. This fast, lossless
CCITT Group 4
compression method is compatible with Acrobat 3.0 (PDF 1.2) and later.
Rotates any page that is not square with the sides of the scanner bed, to make the PDF page align vertically.
Deskew
Choose Automatic or Off.
Whitens nearly white areas of grayscale and color input (not black-and-white input).
Background Removal
For best results, calibrate your scanner's contrast and brightness settings so that a scan of a normal black-and-white
page has dark gray or black text and a white background. Then, Off or Low should produce good results. If scanning
off-white paper or newsprint, use Medium or High to clean up the page.
Removes dark streaks that occur at the edges of scanned pages, where the scanner light is
Edge Shadow Removal
shadowed by the paper edge. Choose Off, Cautious, or Aggressive.
Removes isolated black marks in black-and-white page content. Low uses a basic peephole filter. Medium
Despeckle
and High use both a peephole filter and a large area filter that removes larger spots farther from nearby features.
Removes halftone dot structure, which can reduce JPEG compression, cause moire patterns, and make
Descreen
text difficult to recognize. Suitable for 200–400 ppi grayscale or RGB input or, for Adaptive compression, 400–600
ppi black-and-white input. The Automatic setting (recommended) applies the filter for 300 ppi or higher grayscale
and RGB input. Select Off when scanning a page with no pictures or filled areas, or when scanning at a resolution
higher than the effective range.
When On (recommended), removes excess color at high-contrast edges, which may have been intro
Halo Removal
duced during either printing or scanning. This filter is used only on color input pages.
Scanning tips
• Acrobat scanning accepts images between 10 and 3000 ppi. If you select Searchable Image or Formatted Text &
Graphics for PDF Output Style, input resolution of 72 ppi or higher is required, and input resolution higher than
600 ppi is downsampled to 600 ppi or lower.
• On the Color/Grayscale menu in the Optimization Options dialog box, apply lossless compression to a scanned
image by choosing CCITT for black-and-white images or Lossless for color or grayscale images. If this image is
appended to a PDF document, and the file is saved by Save, the scanned image remains uncompressed. If the PDF
document is saved using Save As, the scanned image may be compressed.
• For most pages, black-and-white scanning at 300 ppi produces text best suited for conversion. At 150 ppi, OCR
accuracy is slightly lower, and more font-recognition errors occur; at 400 ppi and higher resolution, processing
slows and compressed pages are bigger. If a page has many unrecognized words or very small text (9 points or
smaller), try scanning at higher resolution. Scan in black and white whenever possible.
ADOBE ACROBAT 3D VERSION 8
User Guide
67
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