Lets not get confused here. "Brightness" is not dependant on room conditions. It is crucial to set it right . A good rule of thumb if you don't have a disc, etc. is to play a 'letterboxed' movie. You want a black object in the picture section (a totally dark night sky, a black stovepipe hat etc.) to match the black of the letterbox borders. That is why I paid a premium for the OLED TV. If I play a letterboxed movie at night, it is impossible to tell where the picture ends and the letterbox begins. It looks like I bought a 2.35:1 sized TV.
It is the "Backlight" (a 'new' setting for LCD TVs, it didn't exist for CRTs) adjustment is where the room conditions really come into play. Just juicing the overall picture (let's face it, what good's a "perfect" picture if you can't see it with all the shades up and the gang is over watching the World Series?) is less damaging than upping the 'Brightness' so pump the Backlight up (and if you really have to, 'Contrast'/'Brightness', but if you have settings memories, do what I suggested. Set your 'perfect' in very low light and save it, then a pumped up version for bright room light.