Subjective image quality as a function of viewing distance, resolution and picture size

This paper describes two experiments concerning the subjective quality of complex scenes. Slide projections were used as stimuli and they were varied in viewing distance, resolution and picture size. The subjective quality Was judged by a group of twenty subjects by means of categorical scaling. The results of the experiments show that the (angular) resolution expressed in periods per degree and the picture angle spanned by the display, each influence the quality independently. Subjective quality increases with resolution, but saturates at a resolution (6 dB cut-off frequency) of approximately 25 periods per degree. There is also a linear relationship between the subjective quality and the logarithm of the picture angle. In the discussion, these results are compared with those of a number of experiments known from the literature. The results are also interpreted in terms of consequences for High-Definition TV

Perceived sharpness in moving images

\u3cp\u3eTwo investigations were set up into the dependence of the human sharpness impression in complex scenes on velocity and resolution. Sequences, in which a portrait was moving horizontally at a constant speed, were presented on a high-resolution monitor (velocities between 0.5 and 35 deg/s). Both a maximum resolution version and bandwidth-reduced versions were presented. Subjects assessed the (subjective) sharpness of the stimuli on a categorical scale. The results show that for the maximum resolution images, there is hardly any change in perceived sharpness as a function of velocity. Furthermore, for the low resolution images, we find an increase in sharpness with velocity, which implies that the perceived sharpness range is compressed at those velocities.\u3c/p\u3

Evaluation of PALplus proposals

Discusses the evaluations made within the framework of the PALplus group to assess both the PALplus quality and the compatible quality of several candidate algorithms, based on simulations. Since the detailed information is confidential to the members of the PALplus group, the paper focuses on the methodology and on the implementatio