Epson ES-1000C Reference Manual page 117

In the color scanning mode, the data format setting defines tones for
each of the three primary colors, green, red, and blue.
Data format
1 bit/pixel/color
2 bit/pixel/color
3 bit/pixel/color
4 bit/pixel/color
5 bit/pixel/color
6 bit/pixel/color
7 bit/pixel/color
8 bit/pixel/color
Specifying the data format determines the amount of image data in
each data block.
Note:
Even when the specified values exceed the capabilities of the
computer display or printer, data is sent according to the specified
format and quantity. Before scanning, you should consider how the
image data can be stored or processed.
ESC D and other commands
The data format selected by this command determines the effective
halftoning mode selectable with the ESC B command.
With multilevel data settings (more than 3 bits per pixel per color) the
halftoning modes are not effective.
Monochrome
2 grays
4 grays
8 grays
16 grays
32 grays
64 grays
128 grays
256 grays
Color
8 colors
64 colors
512 colors
4,096 colors
32,768 colors
262,144 colors
2,097,152 colors
16,777,216 colors
Command Reference
3-23