The preview datapath contains a data formatter that converts 8:8:8 pixel to RGB 5:6:5 format compliant with the 16-bit format of the LCD controller. In general, when converting from a color channel with more bits to one with fewer bits, the formatter module discards the lower-order bits.
For example, converting from RGB 8:8:8 to RGB 5:6:5, the formatter module discards the three LSBs from the red and blue channels, and two LSBs from the green channel.