I remember reading that brightness should be set correct using the proper pattern and shouldn't be altered to influence gamma. I'm sure someone with more knowledge than me will reply.
Dolby Atmos/DTS:X 5.2.4
Marantz SR6010 + Onkyo M-5010 - Samsung JS8500 - Samsung K8500 - Definitive Technology BP8060, CS8060, SR8040, PM800 - Dual SVS PC12-NSD
2ch: Marantz PM8004 - Oppo BDP-105D - Music Hall MMF-5.1 - iFi iPhono - Airport Express - Monitor Audio Bronze 2