This technical brief provides detailed information on the Image Quality, Performance, and Flexibility of Epson
Image Quality—Factors affecting image quality
When comparing scanners, hardware resolution and color pixel depth are two features often used to gauge
image quality. These two features are important, but there are a number of factors that determine image
quality in a scanner, such as the following: (Many of these elements will be discussed in detail in upcoming
sections of this document.)
Precision stepper motor
for high quality sub-scan
Type of lamp system used
The Epson Expression
lence with respect to image quality, speed, usability, versatility, and durability. These scanners include the
highest quality components.
The Epson Perfection
users, and are designed with the highest quality components in their price class.
A scanner's resolution determines the amount of data that is read by the scanner. As resolution increases, so
does the ﬁle size. Resolution is measured in a variety of ways.
1. Optical resolution: This is the actual number of pixels read by the CCD (Charge Coupled Device), which
measures the intensity of the light that is reﬂected from the image to be scanned, and converts it to an
analog voltage. If a scanner has a resolution of 600 x 2400 dpi, its optical resolution is 600 dpi, which
means that it can resolve 600 bits of data per inch.
2. Hardware resolution: Using a precision stepper motor to double-step or
quadruple-step the carriage, the scanner's sub-scanner resolution can be
increased. For example, a scanner can have an optical resolution of 1200
dpi, but a hardware resolution of 1200 x 2400 dpi (because it double-steps
the carriage to increase the vertical resolution).
Scanner Technical Brief—Page 1
Dynamic range control
and GT series scanners are Epson's professional series scanners designed for excel-
series scanners are designed for home and entry-level corporate and graphics arts
Optical resolution and
color bit depth
Quality of the Analog to Digital con-
verter (ADC); Epson scanners have
optimum performance for minimal
noise and tight color registration.
Type of focus method
Color vs. monochrome CCD