Comparison of HD and UHD video quality with and without the influence of the labeling effect

The past decades have shown a steady rise in the pixel resolution of digital visualization technologies. New TVs and computer displays available on the consumer market are commonly UHD/4K, and 8K recently started appearing in the commercial world. The added value of such higher resolution is not only indicated by the purported level of visual performance, but also by the labels that emphasize the devices’ properties, especially the resolution. However, the genuinely perceived difference between two resolutions, such as HD and UHD, may not have the same effect on user experience as the labels attached to the devices or sequences themselves. In this paper we present four subjective studies in which we investigated the influence of the labeling effect in the context of HD and UHD video. Subjects were shown pairs of either HD or UHD video sequences and had to determine whether there was a difference in quality between the sequences. Two of the subjective tests involved labels in these paired comparisons, indicating to the subject which sequence was which, while the other two tests excluded these labels. For both test sets with and without labels, one test used a 3-point comparison scale for the subjective assessment of visual quality, while the other used a more fine-grained 7-point scale. Our findings show that the sole inclusion of quality labels can strongly impact subjective rating behavior and the overall opinion on UHD quality; also, visual differences between HD and UHD video were rarely noticeable by the subjects.