If you are loosing a noticeable amount of picture by watching your television in 16:9 mode, you must be in a partial zoom 16:9 mode. 16:9 equals 1.77:1. Movies presented in a ratio higher than that will still have black bars above and below the picture on an anamorphic widescreen setup. It is simple geometry.
My projector is permanently set as anamorphic. Material presented at 1.77:1 fills the screen. Above that, black bars top and bottom. Below that black bars right and left. Always the full, entire picture. Non anamorphic DVD's are essentially 4:3 (1.33:1). That means black bars right and left. Problem is, the 4:3 picture is letterboxed so there are black boxes all around (window boxed). That's a whole lot of nothing!!