The main objective of this paper is to verify test methodologies for the assessment of high dynamic range (HDR) video. To achieve this, a next generation HDR monitor by Dolby Laboratories was used to display professionally produced HDR content. Two complementary approaches for subjective assessment of HDR video were then designed and carried out at the European Broadcast Union and Ecole Polytechnique Fédérale de Lausanne premises. Results obtained from both evaluations were highly correlated, which shows that they offer a good degree of reliability and reproducibility in different situations. Analysis of the scores in both cases also shows good confidence intervals for each point under test. Finally, they could demonstrate that an increase in terms of quality of experience can be expected from the conventional level of 100 nits to HDR/high brightness at 4000 nits, with intermediate improvements at 400 and 1000 nits.