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| WHAT IS PREPRESS |
Prepress is the term used in the printing and publishing
industries for the processes and procedures that occur between the creation of
a print layout and the final printing. The prepress process includes the
preparation of artwork for the press, media selection, proofing, quality control
checks, and the production of printing plates if required. The artwork is often
provided by the customer as a print-ready PDF file created for desktop
publishing.
Desktop publishing, or DTP, is the process of editing and layout printed
material intended for publication, such as books, magazines, brochures,
and the like using a personal computer. Desktop publishing
software, such as QuarkXPress, InDesign, or PageMaker is
specifically designed for such tasks. Such programs do not generally replace
word processors and graphics applications but are used to aggregate content
created in these programs: text, bitmap graphics (such as images edited with Adobe
Photoshop), and vector graphics (such as drawings/illustrations made with Adobe
Illustrator).
Processes
Digital prepress
Color matching
Color swatches
1. Binding
selection gives the customer multiple options for the spine of the
publication such as Saddle-stitched, Perfect Bound, or Case Bound,
also Spiral, Wire, and Comb binding are possible. Each
has its merits and suits a particular number of pages.
2. Preparing
artwork involves setting color profiles, bleed, registration, and crop
marks as specified by the printers, using spot colors, trapping, and overprinting as
needed. Check transparency flattening results and allow for creep.
3. Pre-flight is
an automatic scan of the document using the printer's pre-defined profile to
find errors before submitting.
4. Raster
Image Processor (RIP) is the software/hardware that processes the
print-ready files into a rasterized format that the printer can
understand.
5. Proofing involves
creating an accurate copy of the artwork before beginning production runs. This
serves as a bond between the printer and their customer that the final product
meets an agreed-upon standard. Proofs in general can be done for all parts
(images, illustrations, text, and colors) of the print product. In this part,
three types of proofing should be checked and printed out: the print-ready PDF
files, the printer's proof, and the imposition proof. Print-ready PDF files
should be made after the layout using preflight at the printing house. The
printer's proof should be printed out in high resolution and checked by the
customer. The imposition proof, which is usually done by the printers, should
also be printed out to check and adjust the printing press.
6. Soft
proofs are digital proofs that simulate accurately how the finished
publication will look, intended to highlight any future issues.
7. Hard
proofs are physically printed proofs that simulate accurately how the
finished publication will look, intended to highlight any future issues.
8. A Contract
Proof serves as the agreement between a customer and a printer which is signed off before the printing can begin. This can be digitally signed as a
digital contract using services like Acrobat Sign.
9. Quality
control is performed throughout the prepress process but especially after
the proofs are produced.
10. Imposition is
the arrangement of the printed product’s pages on the printer’s sheet, in order
to obtain faster printing, simplify binding, and reduce paper waste.
11. Computer
to plate (CTP) uses a laser to burn the image from a computer file onto a
printing plate. Plates are made of different materials, depending on the needs
of the printing method, usually Thermal, Photopolymer, or Silver-Halogen
(violet) plates are used. They usually have a processing stage in chemicals or
liquid although process-free plates are available.
In
most modern publishing environments, the tasks related to content generation
and refinement are carried out separately from other prepress tasks and are
commonly characterized as part of graphic design.
DIGITAL
PRINTING
Digital
printing allows the printing of a lower volume or individually customized
publications; this is also known as Variable Data Printing (VDP).
Variable Data Printing starts with a static piece of artwork and has an element
that changes which can be fed from a database, such as a customer's name.
Conventional offset printing uses 4 printing plates for CMYK color
publications making it only cost-effective to print thousands of copies of each
version. Digital printing is also cost-effective for an individual publication
with a fast turnaround. Toner cartridges or Inkjet Cartridges are
used making them easy to operate and maintain. Advanced machines have options
for additional spot colors with special inks such as metallic, fluorescent, and
white.
COLOR
MANAGEMENT
Managing color across the process involves having the right equipment and taking regular measurements. You need wide color gamut monitors that can best replicate a CMYK color space and have been calibrated. Pantone swatch guides are needed for color matching. A professional color profiling system like the ones listed at the International Color Consortium (ICC) and using ICC color profiles are required. Spectrophotometers to validate the color of the CMYK ink and spot colors are also important in prepress.
QUALITY
CONTROL
Images in a print-ready PDF should be uploaded at 300 dpi resolution. Any vector artwork or text should stay vector including clipping paths embedded in images for cutouts, as the RIP will rasterize them at 2400dpi, it can take about 10 GB of data to create the rasterized image for the printing plates. Text and vector can print at 2400dpi if it only uses one solid color as there will be no halftone dithering, that's why magazine text is so sharp. Images can only print at the equivalent of 300dpi because of the dithering needed for the gradients and mixed colors, although the dithering of the image is printed at 2400dpi (300dpi for images, and 2400dpi for text and vectors are typical values stated by printers).
All
artwork should be checked for imperfections in resolution, embedded fonts,
color profiles, printer marks, and any obvious mistakes that were missed during
the writing, design, editing, or proofreading stages, although prepress is not
accountable as the artwork should already be agreed as print-ready.
DIGITAL
WORKFLOW
Key prepress digital workflow software products include Agfa Apogee, Fujifilm XMF, Heidelberg Prinect, Kodak Prinergy, and Fiery Workflow Suite. Important features when choosing digital workflow software or cloud submission and proofing software include A version control system that helps you keep track of who is changing what and when. A secure system that lets different people check in and check out files and records when they do so. A method to lock down files currently in use to prevent simultaneous modifications by others. A way to lock out files so that only particular people can open them and change them, but anyone can view them.
HISTORY
During
the 1980s and 1990s, computer-aided prepress techniques began to supplant the
traditional dark room and light table processes, and by the early
2000s, the word prepress became, in some ways, synonymous with
digital pre-press. Immediately before the mainstream introduction of computers
to the process, much of the industry was using large format cameras to
make emulsion-based (film) copies of text and images. This film was then
assembled (planning (UK) or stripping) and used to expose another layer of
emulsion on a plate, thus copying images from one emulsion to another. This
method is still used; however, as digital pre-press technology has become less
cost intensive, more efficient, and reliable, and as the knowledge and skill
required to use the new hardware and especially software have become more
widespread within the labor force, digital automation has been introduced to
almost every part of the process. Some topics related to digital but not analog
prepress include pre-flighting (verifying the presence, quality, and
format of each digital component), color management, and RIPing.
PDF
workflows also became predominant. Vendors of Prepress systems, in addition to
the offset printing industry, embraced a subset of the PDF format
referred to as PDF/X1-a. This industry-specific subset is one version of
the PDF/X (PDF for eXchange) set of standards.
In
more recent years, prepress software has been developed which is designed to
find as many efficiencies in the prepress workflow as possible. These tools are
accessed online, and allow different workers to work on one project at the same
time, often from different locations. Key functionality automates common steps
to reduce errors, reinforce quality standards and speed up production. Examples
include automatically re-folioing pages, digital dummies for soft proofs, live
linking with Adobe InDesign, and pre-flight checking. These tools revolve around
a Flatplan and are used in all sorts of prepress including book,
magazine, and catalog production.
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