Scanner - Technical Brief

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
Optical resolution and
color bit depth
Dynamic range control
Type of lamp system used
Optic system
Quality of the Analog to Digital converter (ADC); Epson scanners have
optimum performance for minimal
noise and tight color registration.
Type of focus method
Color vs. monochrome CCD
The Epson Expression® and GT series scanners are Epson’s professional series scanners designed for excellence with respect to image quality, speed, usability, versatility, and durability. These scanners include the
highest quality components.
The Epson Perfection® series scanners are designed for home and entry-level corporate and graphics arts
users, and are designed with the highest quality components in their price class.
Image Quality—Resolution
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.
Scanner Technical Brief—Page 1
1200 dpi
2400 dpi
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).
Image Quality—Resolution (cont.)
3. Interpolated resolution: Interpolation is a method to increase the resolution of an image. It uses a
complex algorithm to “add” pixels to an image based on the mathematical probability of surrounding
For example, if a scanner has a hardware resolution of 1200 x 2400 dpi, and a maximum resolution of
9600 x 9600 dpi, the scanning software uses interpolation to create scanned images with resolutions
greater than the hardware resolution.
4. Benefits of higher optical resolution: Higher resolution allows you to scan the following types of images without using interpolation. Using actual image data instead of interpolated data results in more
accurate images.
Line Art
When scanning black and white line art, image pixels translate exactly
to the printed dots. Therefore, high resolution is required to capture
and print the sharp lines and edges of an image.
2 x 2.5 inch
image scanned
at 1200 dpi
If enlarged to 8 x
10 inches, effective
resolution: 300 dpi
Enlarging a small original
In order to capture enough detail to enlarge an image, you must
increase the scanned resolution in proportion to the increase in image
size. If you don’t, then you will have to interpolate image data to
maintain the same resolution in the larger image.
Precise pixel editing
Many graphic artists scan images at high resolutions for precise pixel
editing. It is always better to capture the image data when the image
is being scanned and use true image data than to use interpolation if
more data is needed later.
Image Quality—Pixel depth
Pixel depth refers to the number of bits of data captured for each picture element (pixel). Each pixel can
have two states (On or Off); therefore the number of colors or gray scales that a scanner can recognize is
computed by taking the pizel depth as an exponent of two. The following charts lists the number of colors
recognized for each different scan mode.
Scan mode
Number of colors recognized
Bi-level (1 bit per pixel) 2 = 2 colors (black and white)
8-bit gray scale 28 = 256 shades of gray
10-bit gray scale 210 = 1,024 shades of gray
8-bit color (indexed color) 28 = 256 colors
24-bit RGB (8 bits per pixel, per color) 224 = 16.7 millions colors
36-bit RGB (12 bits per pixel, per color 236 = Over 68 billion colors
48-bit RGB (16 bits per pixel, per color) 248 = Over 250 trillion colors
Scanner Technical Brief—Page 2
Image Quality—Pixel depth (cont.)
All Epson scanners have a 42-bit or 48-bit color depth. but some of the models support 24-bit external color
depth, which is the data that is sent from the scanner to the computer. Here are the differences between
output color depth:
Key Differences 42-bit, or 48-bit Internal/ 24-bit External Color 36-bit, 42-bit, or 48-bit Internal and External
Color Depth
How it works The scanner captures 42-, or 48-bit image
data, but “downsamples” an image to
24-bits, keeping the most significant color
The scanner captures 36-, 42-, or 48bit image data and outputs all data to a
software aplication that supports 48-bit
image files (such as Adobe® Photoshop®).
48-bit capture
48-bit capture
24-bit transfer
Image quality Because the scanner captures data that
never could have been read by a 24-bit or
30-bit scanner (such as the detail in dark
areas and slight color transitions), the
scanner delivers more accurate images
48-bit transfer
With a 48-bit image file, you always have
access to full image data, which is especially important to graphic artists and
A greater color bit depth generally results in more accurate color reproduction, smoother gradations with
fewer sudden shifts in color, and detailed shadows and highlights.
Image Quality—Epson ColorTrue® Imaging System
Epson scanners use the Epson ColorTrue II Imaging System which is made up of three main elements
(hardware, optics, and processing) and result in superior image quality with fast processing speeds.
Precise scan carriage
Simultaneous RGB scanning
High resolution CCD
Custom glass lenses
Scanner Technical Brief—Page 3
Pixel optimization
Custom ASIC
Image Quality—Epson ColorTrue® Imaging System (cont.)
Through a combination of these hardware, optics, and processing features, the Epson ColorTrue Imaging
System and Epson ColorTrue II Imaging System deliver scanned images with:
Accurate colors
Smooth gradations
Greater detail in
Smooth edges and
minimal color fringing
Sharp image quality
without distortion
Greater detail in shadows
1. Hardware components: Epson scanners use a precise scan carriage with better motors to achieve subscan
resolutions that are double or quadruple the scanner’s optical resolution. Additionally, Epson scanners
capture Red, Green, and Blue simultaneously, versus other scanners that use one-pass scanning but
alternate Red, Green, and Blue lights for each line of a scan. Epson advantages are:
 Better color registration
 Faster scanning speeds
 Higher quality sub-scan resolutions
Epson Method
(1/2 or 1/4 step carriage movement)
Single-Pass Alternate RGB Method
(1/2 step carriage movement)
Simultaneous RGB Capture
Red Capture
One pass
Green Capture
Blue Capture
One pass
2. Optics: Epson scanners use custom lenses that are designed specifically to work with Epson technology
and the scanner’s CCD. These lenses feature:
 Larger “sweet spot” and precision lenses for reduced distortion
 Accurately aligned lens elements to control sharpness
 Glass lenses (versus plastic lenses used by many competitors)
which offer better reflective qualities, providing greater image
 Better image quality than competitive off-the-shelf lenses
because Epson scanners feature custom-made lenses that
match the CCD.
Scanner Technical Brief—Page 4
Small “sweet spot”
can allow edge
Larger “sweet
spot” minimizes
Image Quality—Epson ColorTrue® Imaging System (cont.)
3. Processing: Many Epson scanners use a custom ASIC (Application Specific Integrated Circuit) for fast
scanning. Key features include:
 Line correction captures and processes full RGB color for every pixel and minimizes color fringing in
subscan direction.
 Zoom capability enables smoothest edges along diagonal or curved lines and achieves higher
interpolated resolution
 On-board memory allows for Auto Area Segmentation (AAS) and Text Enhancement Technology (TET)
processing within the scanner—AAS and TET are independent from PC or Macintosh processing,
allowing the scanner to work with better “raw” data.
Epson Method:
Additionally, Epson scanners have a pixel optimization feature
600 dpi
that uses the full resolution of the scanner’s CCD, even scanning
at a lesser resolution. The benefit of this feature is truer image
300 dpi
 For example, on one of the Epson 600 dpi Perfection
scanners, when scanning an image at 300 dpi, the scanner
still uses all 600 pixels per inch to scan the image, then
averages the data to yield the lower resolution image.
 Some competitive models lower resolution by turning off
some pixels to capture less image data.
Competitive Method:
600 dpi
300 dpi
Image Quality—Color CCD
All Epson scanners use a color CCD which uses a single white light source, instead of a monochrome CCD
and three light sources. The color CCD results in faster scanning speeds and the ability to scan threedimensional objects without producing color “ghosts.”
Key Differences Color CCD
Monochrome CCD
How it works Red, green, and blue are quickly captured
in the color CCD illuminated by a single
light source.
Color CCD
White light
three separate lamps are fired for eachline
of a scan, slowing the scanning speed.
Red light
Green light
Blue light
Result when Single light source allows precise
scanning three- alignment when scanning non-flat
dimensional objects surfaces
Scanner Technical Brief—Page 5
The three lamps can cause misalignment
when reflected from non-flat surfaces.
Image Quality—Dynamic Range
Dynamic range measures the difference between the lightest highlights and darkest shadows that a scanner
can perceive (on a scale of 3.0 to 4.0). The maximum density rating is referred to as Dmax.
A dynamic range measurement is important for
designers who scan transparent media (such as slides,
transparencies, and negatives) because the media
itself generally has a dynamic range of 3.2. Reflective
media, such as a photograph, generally does not have
a dynamic range greater than 2.0.
 A high dynamic range results in scanned images
with superior detail in highlights and in shadows—
especially when scanning transparent media.
Superior detail
in highlights
Superior detail
in shadows
Image Quality—Focus Method
Epson scanners use a fixed focus system, AutoFocus optics system, or a Dual-Focus mechanism.
1. Fixed Focus: With this type of focus system, the lens is set to record everything sharply from a fixed
distance—from the lens to the glass scanning bed. The Epson Perfection and GT series scanners use a
fixed focus optics system. The newest Epson scanners have a fixed focal point just above the surface of the
glass for optimized film scanning.
Epson automatic/manual focus
2. AutoFocus optics system: Epson highest-end graphic
arts scanners use an AutoFocus optics system that can
be used in AutoFocus mode or manual mode. This
system offers these benefits:
 The Epson manual/automatic focus optics system
gives you precised sharpness control, especially
when scanning three-dimensional objects and
 With three-dimensional images, you can pick
your point of focus so that background items are
captured with sharp detail, as shown in the glove
and towel in the images to the right.
 For super sharpness when scanning transparencies
or slides mounted in holders, you can set the focus
to compensate for the 2.5mm distance between the
glass and the slide.
Standard fixed focus
3. Dual-Focus mechanism: One of the Epson Expression series scanners uses a
Dual-Focus mechanism. When using the scanner’s custom film holders to scan
transparent media, you can set the scanner’s focal distance to compensate for the
2.5mm distance between the glass and the media. This method eliminates the
“Newton Ring” problem that plagues less sophisticated scanners. Newton Rings are the circular rainbowcolored patterns that appear in a scanned image, caused by surface tension. This effect is similar to the
rainbows that appear in soap bubbles.
Scanner Technical Brief—Page 6
Image Quality—Dual Lens System
Dual Lens System offers
two lenses for two
different resolutions.
A unique Dual Lens System, available on some Epson
scanners, automatically selects from two lenses for
the desired scan resolution.
High Resolution lens
Some Epson Perfection scanners
offers 4800 dpi optical resolution
with the High Resolution lens.
High resolution lens
Document (8.5”)
Film Area Guide (8”)
Super Resolution lens
For a higher resolution of 6400 dpi,
the Super Resolution Lens can scan
slides and film with the bundled film
holders with a scanning width of 5.9
Super resolution lens
Film Holder (5.9”)
Image Quality—High-Pass Optics
Epson High Pass Optics includes anti-reflection optical coatings and a high reflection mirror.
There is typically a small percentage of unwanted reflection with standard CCD glass which can
cause abnormal ghost images. The anti-reflection optical coating on the CCD cover glass minimizes
this reflection and reduces ghost images.
With a higher reflection rate, film scanning speed is faster.
image quality
Ghost image
Scanned with normal CCD glass
Scanner Technical Brief—Page 7
Scanned with anti-reflection
optical coating
Performance—High-Performance Interfaces
In general, Epson scanners targeted to home and small office users have a USB interface for maximum ease
of use. Epson scanners targeted to corporate and graphic arts uses have USB and/or SCSI-2 interfaces for
maximum performance. An optional interface for some scanners is the IEEE-1394 (FireWire®) interface.
The key differences between the scanner interfaces are:
Key Differences USB 1.1/2.0
SCSI-2 narrow/wide
Direct connection to SCSI
port or installed Fast SCSI
PCI interface card
Direct connection to FireWireready Power Macintosh computers and to any PCI Macintosh
with an Apple® FireWire Kit
PC connection Direct connection to
USB port
Requires Fast SCSI PCI interface card
Direct connection to FireWire
port or an installed FireWire card
Daisy chaining Yes, up to 127 devices
via USB hub
Yes, up to 8 devices
Yes, up to 63 devices
Hot plugging* Yes
Up to 10/20 MBps
Up to 50 MBps
Macintosh Direct connection to
connection USB-ready Macintosh
Performance Up to 1.5/60 MBps
* Hot plugging allows you to attach or detach the cable without powering off/on the scanner or computer.
Most Epson scanners that include a USB port offer the newer USB 2.0 (Hi-Speed USB).
 Hi-Speed USB is backward compatible with USB 1.1, so if you have an older computer with a USB
port, it will work with a new Epson scanner.
 You will see only the highest speeds on your scanner if you have a Hi-Speed USB port on both your
computer and your scanner.
Performance—Batch Scanning
Epson scanning software supports batch
 Without batch scanning, you must scan
each image separately.
Place originals on
the scanning bed
 With batch scanning you can define
customized settings for each framed
original, then capture each one as a
separate file—all with one scan.
Flexibility—Intelligent Negative Scanning
Select and define frames in
the scanner driver, and scan!
With a transparency unit attached, Epson scanners can
scan color negatives (such as 35mm negative strips) and
convert them directly to positive images.
 Some other scanners can only scan positive
transparent media, such as color transparencies
and slides.
Scanner Technical Brief—Page 8
Flexibility—Network Scanning
Newer networkable Epson scanners offer the ability to connect to the network as a device (through a
network card) and don’t have to connect through a specific scan server.
Some other Epson scanners can be shared over a network, using the following procedure:
 Attach the scanner to a single computer on the network.
 Install Epson Scan Server (Windows only) on that computer.
 Install the Epson TWAIN Pro Network scanner driver on all computers that will access the scanner
over the network.
Flexibility—Epson Scan with Epson Easy Photo Fix™ Scanning Software
Epson Easy Photo Fix technology is a combination of powerful elements included in the latest Epson Scan
Epson exclusive Onetouch Color Restoration
instantly (with just one
click!) restores faded and
discolored photographs,
slides and negatives.
Epson Dust Removal instantly
cleans up slides and negatives
— with just one click!
Color corrected
Dust removed and color corrected
Epson Scan Grain Reduction smooths the grain that is sometimes evident at high scanning resolutions.
When you scan a slide or film at a high resolution, the scanner is sensitive enough to pick up the slight
shadows created by the individual crystal structures in the emulsion. When you choose Grain Reduction
in the Epson Scan driver, the driver uses a slight blur effect to smooth out the grain.
Scanner Technical Brief—Page 9
Flexibility—Epson Scan
Epson Scan software differs slightly by scanner model. Different scanners offer three of these four distinct
scan modes to meet the needs of novice, intermediate, advanced, and business users.
 Full Auto Mode:
For the novice user—Epson Scan automatically previews the images and recognizes the document
source and type. This mode then automatically crops, uses the auto-exposure settings to optimize
images, and scans the image.
 Home Mode:
For the intermediate user—allowing adjustments of the basic image settings. Icons represent
common scan settings. Available options include automatic sizing, one-touch color restoration,
brightness and contrast adjustment, and destination/resolution choices. This mode allows the
advanced amateur to select the best of automated features and user-controlled settings.
 Professional Mode:
For the advanced user—many options are available to give you greater control over your scanning.
This mode allows the advanced user to have complete control over many sophisticated elements of
pre-scanning. These elements include the Densitometer (a tool that allows a user to hit a specific
color via numerical data), Multiple Marquee (for batch scanning), and Histogram (to correct tonal
 Office Mode:
For the business user—the Office Mode is helpful when you need to scan a large number of
documents with the same size, using the optional Automatic Document Feeder. You can scan
documents easily and quickly without preview in this mode.
Flexibility—DIGITAL ICE™ technology from Applied Science Fiction™
DIGITAL ICE technology
from Applied Science
Fiction(ASF™) is a scanner
feature that combines
hardware and software to
remove dust and scratches
on film and remove tears,
folds, creases, and deep
scratches on photos. This
feature is not available on
all Epson scanners.
Color photo before DIGITAL ICE
Scanner Technical Brief—Page 10
Color photo after DIGITAL ICE
Flexibility—Epson Smart Panel™ software
Epson Smart Panel allows you to scan and send data directly to an assigned application or to the Epson
photo-sharing site. You can also obtain photos and documents in digital form quickly and easily.
This version of the Epson Smart Panel
includes the following features:
RePrint Photos
Scan and Save
Copy Center
Edit Text
Business Card
Scan for Creativity
Scan to Application
Scan to E-mail
Epson Photo Site
Flexibility—Fluid Mount Accessory
In cases where film holders are not the best solutions for film
scanning, the fluid mount accessory offers:
 Scratch removal from film not supported by DIGITAL
ICE™ technology such as black and white film
 Easy scanning of film that won’t fit into standard film
on the
glass, this
image shows
Newton rings
and scratches.
 Reduction of grain and
prevention of Newton rings
from curved film
Fluid Mount Accessory
using the
fluid mount
accessory, the
scratches and
Newton rings
are reduced.
EPSON is a registered trademark and Exceed Your Vision is a trademark of Seiko Epson Corporation. Epson Expression, Epson Perfection, and ColorTrue are
registered trademarks and Micro Step Drive, Easy Photo Fix, Epson Smart Panel, are trademarks of Epson America, Inc. All other products and brands are
trademarks and/or registered trademarks of their respective companies. Epson disclaims any and all rights in those marks. DIGITAL ICE is a trademark of
Eastman Kodak Company.
©2007 Epson America, Inc.
Scanner Technical Brief—Page 11