If characters are separated, use a lower (darker) setting. If characters are touching, use a higher (brighter) setting. If your scanner has a manual brightness control, adjust it so that characters are clean and well-formed. Or if the text isn’t crisp or drops out, try adjusting scanner contrast and brightness to clarify the scan. If your scanner has the color-filtering capability, consider using a filter or lamp that drops out the background color. These settings can improve the appearance of photographs, but they make it difficult to recognize text.įor text printed on colored paper, try increasing the brightness and contrast by about 10%. At 600 dpi, both scanning and processing typically are about four times slower than at 300 dpi.Īvoid dithering or halftone scanner settings.
Your system may require 50 MB of virtual memory or more to scan the image.
(21.59-by-27.94 cm) result in large images (25 MB) before compression. Pages scanned in 24-bit color, 300 dpi, at 8-1/2–by-11 in. For Adaptive Compression, 300 dpi is recommended for grayscale or RGB input, or 600 dpi for black-and-white input. When Recognize Text Using OCR is disabled, full 10-to-3000 dpi resolution range may be used, but the recommended resolution is 72 and higher dpi. Scan in black and white whenever possible. If a page has many unrecognized words or small text (9 points or smaller), try scanning at a higher resolution. At 150 dpi, OCR accuracy is slightly lower, and more font-recognition errors occur at 400 dpi and higher resolution, processing slows, and compressed pages are bigger. If you save the PDF using Save As, the scanned image may be compressed.įor most pages, black-and-white scanning at 300 dpi produces text best suited for conversion. If this image is appended to a PDF document, and you save the file using the Save option, the scanned image remains uncompressed.
Lossless compressions can only be applied to monochrome images. To apply lossless compression to a scanned image, select one of these options under the Optimization Options in the Optimize Scanned PDF dialog box: CCITT Group 4 or JBIG2 (Lossless) for monochrome images. Also, input resolution higher than 600 dpi is downsampled to 600 dpi or lower. If you select Searchable Image or ClearScan for PDF Output Style, input resolution of 72 dpi or higher is required. Acrobat scanning accepts images between 10 dpi and 3000 dpi.
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