Epson ES-1000C Reference Manual page 137

Explanation:
This command downloads a user-defined gamma correction table to
the scanner. This command is used when suitable gamma correction is
not provided by any of the five gamma correction tables built into the
scanner.
Specify ''m'' or ''M'' for the i parameter when defining a gamma
correction table for monochrome scanning, or when setting the same
gamma correction tables for all color component colors (red, green,
and blue). When defining different gamma correction tables for each
component color for color scanning, specify a value for i (''r'' or ''R'';
''g'' or ''G''; ''b'' or ''B'') that is appropriate for the applicable color.
Note:
The brightness command is ineffective when a gamma table defined
with this command is selected by the ESC Z (Set gamma correction)
command.
G am m a t abl e
Index data
0
1
2
3
.
.
.
FF
Output data
d0
d1
d2
d3
.
.
.
d255
Command Reference
3-43