Epson GT-6500 EN - Manual (Page 27)

Functions
EPSON scanners feature a number of various functions. A brief
overview of these functions is provided below. For more detailed
explanations, see the following chapter on using these functions, as
well as the command reference section.
Image definition
Brightness
This function allows you to set the brightness at which images are
scanned. The following illustration shows the difference this setting
can make in the final scanned image. Setting the brightness to a
brighter setting results in a bright image in which some thinner lines
may be washed out. On the other hand, setting brightness to a darker
setting results in a blacker image in which some intricate details may
turn out completely black.
Dark Bright
Overview 1-13