ELSA ERAZOR III LT, User Manual

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All about graphics
ELSA ERAZOR III Pro and ELSA ERAZOR III LT
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video memory is thus not a color value, but only a pointer to a table in which the actual
color value is found. The advantage of this method: Only 8 bits need to be stored for each
pixel, although the color values are 18 bits wide; the disadvantage: Only 256 colors can
be displayed simultaneously from a palette of 262,144 possible colors.
DirectColor
The situation is different in the case of DirectColor (TrueColor, RealColor and HighColor).
In this case, the value stored in the video memory is not translated but is passed directly
to the D/A converter. This means that the full color information must be saved for each
pixel. The meanings of the terms RealColor, TrueColor, and HighColor can be confused,
as they are not always used unambiguously.
HighColor and RealColor
HighColor and RealColor usually describe a 15 or 16-bit wide graphics mode, while True-
Color should only be used for the more professional 24-bit mode (or 32-bit) mode.
15 bits provide 5 bits each for the red, green and blue values, resulting in 32 levels per
RGB component and thus 32,768 (= 32 x 32 x 32) different color hues.
The 16-bit graphics modes are organized differently. Most common are (R-G-B) 5-6-5
(e.g. XGA) and 6-6-4 (e.g. i860). 5-6-5 means that 5 bits are used for each of red and
blue and 6 bits are used for green. In the case of 6-6-4, 6 bits are used for red and green
and 4 bits for blue. Both ways of assigning the bits correspond to the color sensitivity of
the human eye: this is highest for green and lowest for blue. 65,536 different colors can
be displayed.
TrueColor
The TrueColor mode is more complex, using 24 bits per pixel. Here, 8 bits are available
for each color component (256 levels), resulting in 16.7 million different color hues. There
are more colors available than pixels on the screen (1.3 million pixels at a resolution of
1280 x 1024 ).
VESA DDC (Display Data Channel)
The Display Data Channel provides a serial data channel between the monitor and the
graphics board, as long as both support DDC and the monitor cable includes the addi-
tional DDC wire. This feature allows the monitor data to be sent automatically to the
graphics board (e.g. name, type, max. horizontal frequency, timing definitions etc.) or
even for the graphics board to send instruction to the monitor.
There are various standards; DDC2B and DDC2AB.