The demand for better image quality becomes higher and higher, and has been the focal point in the field of image processing with the rapid development in imaging technology. Many factors affects the image quality. Three of the most important factors are “Color”, “Tone” and “Sharpness”. “Image Sharpness” would effect the visual perception on image quality directly. It is a very important factor to be considered when optimizing the image quality. Traditionally, Sharpness adjustment is only emphasized in the image post-processing stage.
This study aims to investigate how the sharpness affected the image quality by using a high-end flatbed scanner to scan color positive film and then adjusting the image sharpness both in the scanner setting as well as in Photoshop Unsharp Mask setting, and identifying the image quality by visual assessment.
The pair-comparison method derived using Thurstone’s Law of Comparative Judgment is used in this study as visual assessment to establish interval scale for image quality index. The image sharpness visual preferences showed an “Inverted U“ shape, which means the most appropriate setting can be found on the peak. The experimental results indicated that the image needed to be sharpened both in the scanning and the post-processing stages. Regression equations were also derived between the image sharpness adjustment and the visual assessment as a reference to adjust the image sharpness.
