Subjective Ranking of Facsimile Document Quality Scanned at Different Resolutions

This study was conducted to ascertain whether the perceived quality of document facsimiles changes when the original documents are scanned at different resolutions. Ninety-six office workers (4.8 male and 4–8 female) were asked to rank three types of documents transmitted at three different scanning resolutions (plus the original) according to their impression of overall quality. The experimental materials were 8 1/2 × 11 inch copies of single-page, black-on-white documents that had been scanned at resolutions of 200 lines per inch (lpi), 300 lpi, 400 lpi, and infinity (original document). The document types were 1) a standard business letter, 2) a line drawing of a ship, and 3) a page from a French scientific journal. The subjects' task was to rank all four copies of a particular document type from worst to best quality. Each subject eventually ranked every document type, but ranked the copies of one document type before going on to another. The subjects were not told that there was any resolution difference among the facsimiles, nor were they told the copies were made with facsimile equipment. The results of the study indicate that experienced office workers' criteria for document quality is highly correlated with facsimile scanning resolution. The document type had a significant effect on subjective quality rankings.