In this paper the influence of ambient light and peak white (maximum brightness) of a display on the subjective quality of videos shown with local backlight dimming is examined. A subjective experiment investigating those factors is set-up using high contrast test sequences. The results are firstly analyzed with an ANalysis Of VAriance, which shows significant effect of the Sequence and Algorithms interactions and the Peak White and Ambient Light interactions. This latter allows us to define test cases for which the peak white and ambient light are adapted to one another. An objective model of the subjective grades is then computed using Partial Least Squares regression that achieves 0.68 correlation.