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Imaging |
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Document imaging includes
many critical aspects of the scanning process. There
are many criteria to consider when scanning documents
such as image density, Color, Grayscale or Bitonal.
We will help you evaluate your final products needs
to determine the best imaging criteria. Here are
some detailed subjects related to imaging: |
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| 1. |
Job Evaluation |
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The following issues should
be evaluated before you begin to scan:
- Image Quality (Sharp,
Good, Poor)
- Print Types
- Handwritten,
Typewriter,
- Impact, Ink Jet,
Laser, etc.
- Photo Images
- Paper Type
- Onionskin, Transparencies,
Recycled, glossy, etc.
- Various paper sizes
Image quality, paper and print
type can provide useful information with
respect to your decision to use or not use
scan technology on your job.
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| 2. |
Image Quality |
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Document scanners typically
produce a black and white (bitonal) image.
Grayscale scanning generally is not employed
because file sizes are orders of magnitude
larger than bitonal file sizes.
The decision to use document
scanning is based on whether a bitonal rendering
of your paper is satisfactory. The answer
is a simple "yes" where the paper
is white and the text is black. More careful
consideration must be given to documents
like invoices, on which gray backgrounds
with red and green color boxes are common.
Photos and text documents with photos require
sample output and client approval of acceptability.
Image quality is a function
of selecting the appropriate scanner to
do the job. Some scanners render black text
on white paper flawlessly but do a very
poor job where colors or grays are part
of the requirement. Other scanners handle
very difficult gray and color requirements
nicely using a process called dynamic thresholding.
Some scanners allow two or more images to
be captured from a single piece of paper.
Scanners that capture more than one image
usually capture the whole page at a low
resolution and other, selected images at
much higher resolution.
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| 3. |
Paper Handling |
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Different scanners utilize
different paper transports including belts,
ball bearings and rollers. Auto-feeders
use various techniques to provide continuos
feed and have different limitations with
respect to methods used. How a scanner handles
paper has a direct impact on its suitability
for a particular project. Many scanners
cannot handle onionskin, card stock or batches
of mixed paper widths and weights. Some
scanners cannot handle small paper, or paper
wider than 8.5 inches.
Like image quality, fast,
efficient paper handling depends on selection
of the right scanner.
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| 4. |
Image Resolution |
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Image resolution determines
the number of pixels or dots, per linear
inch. Popular resolutions include 200, 240
and 300 dpi. 400, 600 and even 1200 are
available.
A 300 dpi resolution renders
300 dots per inch. Higher resolutions generally
improve image readability. Many monitors
display images at 72 dpi, regardless of
the resolution at which they were scanned.
High-resolution monitors display images
at approximately 200 dpi. Most monitors
require you to "zoom in" on the
image to view the resolution actually available.
Printers can only produce print images within
their dpi range. A 600 dpi high-resolution
image will only print at 200 dpi when printed
by a printer only capable of 200 dpi resolution.
Scale-to-gray technology using
techniques like dithering can make images
more readable. The dithering process uses
extrapolation techniques to improve resolution.
Image resolution will significantly effect
image file sizes. For instance, the file
size of a compressed TIFF Group 4 compressed
image at 200 dpi might be 60 KB, while it
might be 90 KB at 300 dpi.
Resolution recommendations
will be evaluated on the level of detail
required to capture all needed substantive
data from the paper while minimizing file
sizes.
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