Evaluation of perceived image sharpness with changes in the displayed image size

In this paper an evaluation of the degree of change in the perceived image sharpness with changes in displayed image size was carried out. This was achieved by collecting data from three psychophysical investigations that used techniques to match the perceived sharpness of displayed images of three different sizes. The paper first describes a method employed to create a series of frequency domain filters for sharpening and blurring. The filters were designed to achieve one just-noticeable-difference (JND) in quality between images viewed from a certain distance and having a certain displayed image size (and thus angle of subtense). During psychophysical experiments, the filtered images were used as a test series for sharpness matching. For the capture of test-images, a digital SLR camera with a quality zoom lens was used for recording natural scenes with varying scene content, under various illumination conditions. For the psychophysical investigation, a total of sixty-four original test-images were selected and resized, using bi-cubic interpolation, to three different image sizes, representing typical displayed sizes. Results showed that the degree of change in sharpness between images of different sizes varied with scene content