High Definition Television (HDTV) is the new broadcasting system designed to take the place of Standard Definition Television (SDTV) at home in the near future. This system requires modification of many features in the broadcasting chain with an overall objective of reaching a noticeably higher quality of experience. Since broadcasters desire a high level of service acceptability, they require efficient measurements of quality of experience. The purpose of this paper is to provide such measurements concerning the noticeable artifacts in H.264 distortions over a range of display sizes and comparing HDTV to SDTV. A subjective characterization of some HDTV quality of experience aspects is proposed and the results are discussed.