This paper presents a subjective experiment performed to determine the optimal level of sharpness enhancement for various image content and two display technologies. For the experiment, a peaking algorithm was used as sharpness enhancement method and its gain parameter, which controls the amount of sharpness enhancement, was optimized. Eleven still images were used as image material, and for each original, eight levels of sharpness enhancement were shown. Subjects were asked to select the image that they prefer most on overall image quality. To study the effect of the display technology, the experiment was performed on a CRT monitor and LCD panel. The results show an effect of content: lower gains were preferred for faces and content with flat areas, while higher gains were preferred for highly textured images. We also found an effect of display: in general for a given image, the averaged gain preferred on the CRT was equal or higher than on the LCD. The results can be used to optimize sharpness enhancement algorithms to image content and display type in agreement with the averaged preference of viewers.
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