Amiga Graphics Archive

Extra Half Bright (EHB)

This is a screen mode where the Amiga could display 64 colors on screen.

The primary limitation was that, despite being able to display 6 bitplanes (2^6 = 64 colors), the Amiga only had 32 color registers to define the color palette used for that sceen. This would have meant that only half of the palette would have been changeable. The other half would have had to be predefined or otherwise overloaded.

Creating shadows

The trick that was used was to set the top half of the palette to the same color values as the bottom half but only at half the brightness. This was done by right shifting the bit values of the lower half values when copying them to the upper half colors.

Bullfrog - Fusion

Bullfrog's Fusion showing semi transparent drop shadows underneath all objects.

PaletteColorPercentageHexBinary
color #01  100% 033% 013% F 5 2 1111 0101 0010
color #33  050% 013% 006% 7 2 1 0111 0010 0001

This was a great method to create shadow effects as the sixth bitplane would always make everything half as bright as it was without it.

Only few games utilised this feature probably because using six bitplanes was putting such a strain on the graphics memory and the blitter that it was deemed to expensive for the result that was achieved.

Getting the most out of it

Deluxe Paint IV - EHB default palette

Deluxe Paint IV used this default palette for EHB images. It is clearly visible that the right half of the palette is only half as bright as the left half.

While being nice for shadow effects it was a very different matter if you wanted to get the most out of all 64 colors.

The Deluxe Paint palette is a good example for this because if we rearrange the colors it becomes clear that it is acutally quite smart.

 

Deluxe Paint IV - EHB default palette

By placing all bright colors in the lower half of the palette these colors are then available in the upper half of the palette as dark versions. This enables the artist to have full gradient of a color despite only being able to define half of its colors.

This is extremely difficult to pull off because in reality not all palettes can be split up to utilise this feature.


Psygnosis - Agony

Psygnosis' Agony loading screens featured the awesome art of Franck Sauer.

The loading screens in Agony are a prime example of EHB images. The ammount of colors and gradients used in the image is simply astonishing and must belong to the best that have been done on OSC Amigas.