Grayscale; Color - Microtek ScanMaker IIG User Manual

Grayscale

Grayscale images contain more than just black and white, and
include actual shades of gray. In a grayscale image, each pixel or
dot has more bits of information encoded in it, allowing more
shades to be recorded and shown.
For instance, four bits are needed to reproduce up to 16 levels of
gray. Going higher, eight bits can reproduce the 256 levels of gray
required to represent most black-and-white photos accurately.
16 grays

Color

Color images contain the most complex information. To capture
color images, scanners use a process based on the RGB (Red,
Green, and Blue) color model, where every color is composed of
a varying amount of the three colors. In the RGB model, the
absence of white light creates black, the complete saturation of
light creates white (100% of red, green, and blue), and equal
amounts of red, green, and blue create intermediate shades of
gray.
Depending on the type of scanner you have, your scanner can
record 24 bits or 36 bits for the three RGB channels. This means
your scanner can record and reproduce an enormous amount of
color information — anywhere from 16.7 million colors for 24-
bit scanners, to 68.7 billion colors for 36-bit scanners. The extra
amount of information that can be processed by 36-bit scanners
translates to more vivid color reproduction, as the scanner is able
to accommodate more subtle gradations of color approaching
lifelike accuracy.
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256 grays