The main objective of this paper is to verify test methodologies for assessment high dynamic range (HDR) video. To achieve this, a next generation HDR monitor by Dolby Laboratories was used to display professionally produced HDR content, including some scenes from recently released movies. Two complementary approaches for subjective assessment of HDR video were then designed and carried out at the EBU and EPFL premises. Results obtained from both evaluations were highly correlated which show they offer a good degree of reliability and reproducibility in different situations. Analysis of the scores in both cases also show 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 4'000 nits, with intermediate improvements at 400 and 1'000 nits.