The Brightness control is one if the most mis-understood settings, it's true function is to set the black point of the video
signal or where the lowest piece of video signal is visually seeable.
Because of this mis-understanding a user can set the value too high in an attempt to create a brighter picture.
As you can see in the example the image is washed out and lacking shadow detail. The dynamic range or contrast ratio is
also diminished, and depending on the display design can cause clipping of the white levels, which ironically is the opposite
of the intension of trying to set the image brighter.