Flatbed Notes

Scan examples

These descriptions are here because a visual fault is easier to name once you have seen it once. I used office scrap paper and expired forms for the examples, not private documents.

Vertical streak

A single line of dirt on the calibration area can become a full-height streak in every scan. Clean the narrow white strip near the glass edge, not only the main bed.

Dust and speck contamination

Dust is worst on high-contrast bilevel scans. A pale speck becomes a black island, then OCR treats it as punctuation. Clean, rescan, and compare the same crop at 300 DPI grayscale.

Lid shadow

Thick packets and bound manuals cast a gray edge that automatic exposure may preserve as if it were part of the page. The shadow can pull deskew tools away from the true text baseline.

Overexposure

Old carbon copies and pale blue handwriting disappear quickly when a driver is set for "text." Scan them as grayscale photographs first, even if the final access copy will be black and white.

JPEG damage

JPEG blocks around type look harmless until the page is enlarged or OCR sees the blocks as part of a letter. Use TIFF or PNG for working copies. Make small JPEGs only for web display.

Example contact sheets were once on this page. Removed in 2006 after a hosting quota warning.