So, how bright should your bias lights be?
There is an answer. The perceived level bouncing off the wall behind the TV (taking into account how dark the wall is) should be 10% of the maximum brightness of your TV*
*In SDR mode -- the jury is still out on the best HDR levels, but since much of HDR is specular highlights, 10% is still a safe bet.
Play or cast this pattern on your TV with the TV's brightness settings adjusted for dark room viewing (lower brightness than bright room viewing). The bounced lights off the wall should not look brighter than the gray rectangle in the center of the screen, but they can be dimmer. Here is a direct link:
Thanks to The Very Nice Interesting Singer Man for creating the MediaLight Theme Song. Read about him here. :-) Sounds like a hit to us!