Adobe 62000112DM User Guide - Page 74

ADOBE ACROBAT 3D VERSION 8 67 User Guide 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.) Monochrome When scanning black-and-white or monotone images, select one of the following: • JBIG2 Applies the JBIG2 compression method to black-and-white input pages. Settings of 0.95 or higher use the 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. • Adaptive (As described above, under Color/Grayscale settings.) • CCITT Group 4 Applies CCITT Group 4 compression to black-and-white input page images. This fast, lossless compression method is compatible with Acrobat 3.0 (PDF 1.2) and later. Deskew Rotates any page that is not square with the sides of the scanner bed, to make the PDF page align vertically. Choose Automatic or Off. Background Removal Whitens nearly white areas of grayscale and color input (not black-and-white input). 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. Edge Shadow Removal Removes dark streaks that occur at the edges of scanned pages, where the scanner light is shadowed by the paper edge. Choose Off, Cautious, or Aggressive. Despeckle Removes isolated black marks in black-and-white page content. Low uses a basic peephole filter. Medium and High use both a peephole filter and a large area filter that removes larger spots farther from nearby features. Descreen Removes halftone dot structure, which can reduce JPEG compression, cause moire patterns, and make 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. Halo Removal When On (recommended), removes excess color at high-contrast edges, which may have been intro­ 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.