Color Electronic Prepress Systems
Computers are increasingly present in the work space and many commands
have access to digitized systems producing finished graphics. Digitization is
also used in the creation of color separations for reproduction. You should
be aware of color electronic prepress preparation and some of the serious
limitations it imposes.
Color Electronic Prepress Systems (CEPS) are high-end systems that perform
all the steps required to create original art and transfer it to a press plate. A
CEPS is a component system containing a drum scanner, a digitizing tablet
with a cursor or tracing pen, memory, software, a high-resolution color
monitor, and an output device to record images.
Image and color resolution are primarily controlled by the type of scanner
used to scan images. Most CEPS have a drum scanner that scans at high
resolution. Images scanned by the drums of CEPS scanners may be imported
to a desktop computer system for manipulation and exported back to the
CEPS system for final resolution before printing. CEPS drum scanners
rotate at high speed. A beam of light passes through or is reflected from
copy. An internal photomultiplier tube (PMT) records the image. There is
an individual PMT to record each blue, red, and green signal.
electronic signal is fed to four separate internal computer units (blue, red,
green, and black) for color correction. Signal ranges may be manually
changed for effect. Corrected signals are then fed to lights that vary intensity
to correctly expose film. CEPS scanners accommodate all line art, grey scale
scanning, and color.