nfaguys, BTB is the ability for a display/source component to pass below black. If you have a copy of DVE - Digital Video Essentials - you can do the PLUGE pulse test to see if your display shows Blacker than black. There are 3 pluge pulses with the outer one being BTB. It's an easy way to adjust brightness. You turn down the brightness until the BTB pluge pulse just disappears. The THX optimizer akso has a BTB pattern. It's the shadow of the THX logo.

That sets your display at optimum brightness. Some argue that it is not necessary to be able to display BTB; I like it because it makes adjusting brightness a snap for me.