Perhaps Mingus can clarify this, but the OP use of the word "screen" seems clearly to be referencing a projection screen, not a television or monitor. If that truly is the case, then all the carrying on about back lighting or bias lighting the screen is nonsense. If the case is that it's a TV or monitor, then things are different.

Those who use TVs or monitors in their systems are well advised to do what many recommend and give their eyes some help. OTOH, if you're using a projector and screen, It's complete and utter nonsense to think about backlighting or bias lighting your projection wall.

In the home theater (similar to a commercial theater) where one is using a projector and AT screen, the notion of backlighting is beyond ludicrous.