Amiga Halfbrite mode

Extra Half Brite (also referred to as Extra-Half-Brite or Extra-Halfbrite) usually abbreviated as EHB,[1][2][3][4] is a planar display mode of the Amiga computer.

Normal 32 color mode picture

Extra Half Brite 64 color mode picture

This mode uses six bitplanes (six bits/pixel).[3][5][6] The first five bitplanes index 32 colors selected from a 12-bit color space (4096 possible colors). If the bit on the sixth bitplane is set, the display hardware halves the brightness of the corresponding color component.[7] This way 64 simultaneous colors are possible (32 arbitrary colors plus 32 half-bright components) while only using 32 color registers.[8] The number of color registers is a hardware limitation of pre-AGA chipsets used in Amiga computers.

Some contemporary game titles (Fusion,[9] Defender of the Crown[10], Agony,[11] Lotus II[12] or Unreal[13]) and animations (HalfBrite Hill[4]) used EHB mode as a hardware-assisted means to display shadows or silhouettes.[9][14] EHB was also often used as general-purpose 64 color mode with the aforementioned restrictions.[9][15][16][17]

Some early versions of the first Amiga, the Amiga 1000 sold in the United States lack the EHB video mode, which is present in all later Amiga models.[4][2]