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WILL GHOSTING BE A PROBLEM?
WHAT IS A GHOST?
A ghost is an image - unplanned and unwanted - that is
a result of the printing system itself. A ghost should not be confused
with set-off or show-through.
The evolution of printing
technology has increased the opportunities for ghosts to occur.
Today's greater service demands the "work-and-turn" format,
and the development of quickest inks have all contributed to the
problem.
STARVATION GHOST
This ghost appears in large solids or dense halftones either
as a light or a dark print of another part of the form. If part
of the form contains block letters or other solids of a size to
strip sufficient ink from the form rollers, and if this part is
next to the solid and on the gripper side of it, the letters appear
as a light-print ghost in the solid or halftones.
If, on the other hand, the
block letters are reverses near the gripper edge of a large solid,
they will print as dark ghosts in the solid because the reverse
leaves excess ink on the form rollers. Thus, these ghosts repeat
in the same inking channel, gradually fading out toward the tails
of the form.
The basic cause of this
ghost is the layout of the form combined with the overtaxing of
the presses inking capability.
BLANKET GHOST
This is the result of a previously used blanket having a swollen
or a depressed image area caused by use on another job. If either
of these areas falls within the halftone, screened tint, or solid
parts of the form being printed, they will cause printing to appear
different from the surrounding area - darker if the blanket is swollen
and lighter if the blanket is depressed. Excessive impression causes
the darker print and too little impression causes the lighter.
PLATE GHOSTS
There are two varieties of plate ghosts, both found in offset lithography.
The first kind has nearly disappeared from the scene because it
is caused by poor regraining of a previously used plate. The old
image is not completely removed and begins to make an appearance
on the new job, conflicting with the new form.
The second type of plate
ghost occurs on multicolor presses where the form on one of the
color units sensitizes the plate of the following color unit. Proper
desensitizing of the affected plate and ink adjustments correct
this situation.
CHEMICAL GHOSTS
These ghosts are related to the chemical activity of inks as they
go through their normal drying phases. The appearance of chemical
ghosts is normally unpredictable and more sporadic than that of
mechanical ghosts, becoming evident only after printed sheets have
been in the delivery pile for a period of time.
Chemical ghosts may appear
as sharp of fuzzy reproductions of one side of a form, or one part
of a form, in the solid area of another part. They may appear erratically
- showing up in one printed area of a sheet but not in a similar
or duplicate part.
They are usually in evidence
as a dull ghost on a relatively glossy background or a glossy ghost
on a somewhat duller background.
PAPER EFFECTS ON
GHOSTING
Paper is not a causative factor in ghosting even though
both mechanical ghosts and chemical ghosts appear more distinct
on smooth-coated papers than on uncoated or fancy finish papers.
Just as a smooth-coated paper shows the detail of a print more sharply,
it shows a ghost more clearly and reflects more distinctly the variations
in gloss an dull areas of an ink film Uncoated papers do not show
ghosting patterns so distinctly. Nevertheless, ghosting patterns
- that are distinct enough to be objectionable - do appear on uncoated
papers.
Taken from "Ghosting" by the S. D. Warren Company
DIGITAL PROOFING: COMING OF AGE
Excerpts taken from DIGITAL PROOFING: THE FAULT LIES IN OURSELVES by George W. Leyda
Proofing is a quality-control
process - a check on other parts of the process and therefore not
a part of the process. Logical thought will agree that the "proof"
is that which in fact "verifies" whether or not the "important
parts" are produced properly. In fact, a final, composed contract
proof is probably the first time that the document creator (art
director, print buyer, etc.) has seen all of his/her ideas and images
in final form. As such, the job can now be corrected, improved,
or approved, which is the very reason it is called a "contract"
proof. This is the first of the most important definitions of the
proof - a visual representation of the expectations of the document
creator or buyer which can be approved as a contractual statement.
On the other end of the
process, how often do we hear the production people at the ad agency
complain about the cost of the proof? "Why should we have to
pay for an expensive proof? We already gave them a file that was
right and a color print!" Of course, this false notion gives
rise to the second most important definition of proofing - to serve
as a communication vehicle (visual guide) so press operators can
be sure they know what the creator/buyer really wants in terms of
color and composition.
Since the early 1960's when
3M Color Key was introduced, color proofing has led the industry
in fostering the development of better and more color printing.
The development of new and better color separation systems were,
if not totally facilitated by the existence of good off-press proofing,
at least greatly expedited by it.
If proofing is so important
yet so disdained by the craft, what do we now have in the digital
world, and where are we in coming to grips with the industry's needs
and the available technology?
No one contemplating a computer-to-plate
workflow would disagree that proofing is vital to the success of
a totally digital workflow. Every conference seems to make time
to discuss the various needs or offerings of digital proofing devices
or methods for remote proofing. Along with the ability to send images
and complete jobs instantaneously by various means where is the
ability to "prove" what you have sent or communicate what
you really want printed? Good, quick, verifiable digital proofing
is the only answer we know of to date, and everybody is clamoring
for it.
To understand the real needs
in proofing today, let's review the reasons for its success in the
past (the analog era). Most successful analog proofing systems were
relatively consistent from proof to proof. Plus, the number of system
configurations to contend with was limited. In addition, even though
we could change the film after the proof was made, it wasn't really
to anyone's advantage to do so. Therefore, when this was done, the
difference in the proof as it was seen and approved by the buyer
was not significant, and printers could therefore feel confident
that the proof was what the customer wanted to match and that the
films they received would allow them to do so. In addition, a visual
check of the films against the proof could always be used in case
of discrepancy. Since the dots were there, it was relatively easy
to see and verify any changes if they existed.
On the front end of the
process, there were no systems that showed a color proof (or print)
unless the film also existed. Thus, the document creator (art director/production
director) had only a proof made from the film to view.
Contrast that scenario with
today's capabilities. Digital proofing, as it is perceived, can
match anything! Anything you can do with Photoshop, you can do with
a digital proof. The perception is that the file, which is now the
"original" (or the "film" in digital terms)
can be manipulated before or after the digital proof has been made
and approved. There is no question that this "file" can
be manipulated, but this is no more true than the fact that films
could be manipulated. Post-proof changing is still just as counterproductive
as before and is still not to anyone's advantage.
Let's look at the existing
technology. There is dot and no-dot, inkjet, thermal dye sublimation
and continuous inkjet, laser ablation transfer, thin-layer thermal
transfer, and photographic material imaged with a laser - probably
a few more - all with several versions. All have been touted as
being the solution. Some have touted one over the other - and have
been proven wrong by the "experts" when the particular
"technology" they didn't think would work proved to produce
a "very matchable" proof. While the various technologies
have monetary and speed capabilities that prove one or the other
to be more or less suitable in a given situation, it is certainly
not safe to assume that a particular technology cannot or will not
be the proof of choice.
Over the past four years,
GATF's Gallery of Digital Proofing analyses have shown that technology
is not a good criteria for "grading" a system. There is
now no doubt that many digital proofing systems can both "show
the creators what they want" and "give press operators
something they can match."
On the other hand, the controlling
factor is being shown to be the image or color management software
that has been married with a particular technology. There are several
examples, but the most recent and readily admitted is the Epson
9000 printer or "proofer." As sold by Epson, the device
is a printer and is having a lot of success as such. As advertised
and controlled by DuPont Color Management software, it is also gaining
credibility as a proofing device.
The technology is here to
go totally digital, and the technology doesn't really matter. How
many firms are using an existing dot-matrix system to proof and
accepting the results with glee at the savings in both time and
money? Their color might not be "cosmetic" color, but
depending on the application, it is certainly sufficient to convey
the two reasons for proofing:
1. Provide document (product)
creators with a reproduction that they can see and approve.
2. Provide press operators
with a visual reference that they have a chance of matching on press.
Also, today's digital proofs
can be changed a lot more easily than the analog systems.
ROCKY MOUNTAIN PRINTING IN THE NEW CENTURY
Rocky Mountain Printing
is pleased to announce the purchase of a Heidelberg 6-color, 40-inch
Speedmaster Press. Starting June 1, 1999, we will be able to produce
jobs that are larger and require more colors. This press is one
of the largest and highest quality presses in the area; we will
be able to print up to a 28x40 sheet of paper. This 6-color has
many state-of-the-art features including the Heidelberg Computer
Print Control System. Also, with the larger rollers on the Speedmaster,
ghosting is a much smaller problem than on other presses.
Because many national printers
and paper manufacturers consider the EPSON STYLUS PRO to be the
best digital proofing machine on the market, we decided it was the
perfect machine for Rocky Mountain Printing. We have calibrated
the Epson to our presses and are amazed at how close we can come
to matching the proofs on press. Now you have the best of all worlds
with RMP: (1) You can look at accurate color proofs before you spend
the money to output film, and (2) Our digital proofs cost much less
than laminated proofs.
Developed with professional
graphics users in mind the Epson Stylus Pro digital proofing system
includes a high-performance external EFI Fiery Adobe PostScript
3 server (RIP) as standard equipment. With the power to simultaneously
spool, RIP, and print jobs over the entire network from both Macintosh
and Windows platforms, the Epson Stylus Pro will yield incredible
production time savings over current digital color proofing systems.
At the heart of the system
is Epson's new Micro Piezo DX3 print head technology, accessing
four high-capacity ink cartridges to produce a level of print quality
unmatched by conventional dye-sublimation and more expensive continuous-tone
devices. Never before has a digital color proofing system offered
unsurpassed Photo Quality with text and line-art that rivals an
imagesetter in output quality.
As a complete pre-film solution,
the Epson Stylus Pro incorporates a professional level color management
system that gives complete control over the CMYK process.
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