Professional Printing(& Prepress)

What is Digital Printing?Modern printing methods such as laser and ink-jet printing are known as digital printing. It is a method where  digital-based images are printed directly to paper. In digital printing, an image is sent directly to the printing machine using digital files such as PDFs and those from graphics software such as Illustrator and InDesign. Much like your desktop print, professional digital printers are, however, lots bigger and faster.

Digital print shops handle high volume digital print jobs

Digital process eliminates theneed for a printing plate, which is used in offset printing.

What is Offset Printing?Offset printing is a printing technique where the inked image is transferred (or "offset") from a plate to a rubber blanket, then to a substrate surface, normally paper. When used in combination with the lithographic process, which is based on the natural antipathy of oil and water, the offset technique employs a flat image carrier on which the image to be printed obtains ink from ink rollers, while the non-printing area attracts a water-based film (called "fountain solution”), keeping the non-printing areas ink-free.

What is Web Printing?• Web offset is a form of offset printing in which a continuous roll of paper is fed

through the printing press. Pages are separated and cut to size after they have been printed. Web offset printing is used for high-volume publications such as mass-market books, magazines, newspapers, catalogs and brochures.

Offset or Digital: Which is best?

Each type of printing method has its own pros and cons.

Offset Printing Pros Ability to print larger quantities cost effectively Can print on a variety of surfaces. And use special colours where four color process is not able to reproduce the required shade. Can better accommodate large runs You can include varnishes, diecuts, embossing Has a richer look and can accommodate more paper types

Offset Printing Cons The process requires more time for work to dry before finishing Costs more than digital presses for low runs Slower turnaround times More expensive

Digital Printing Pros Faster than lithographic printing for smaller quantities Can print in small quantities – ideal when not needing bulk runs of printed material More accuracy on prints when compared to the original design Each print can be customised and can be different in any way from the previous copy

Digital Printing Cons Although much improved over recent years, digital printing quality is still inferior to lithographic offset printing Can’t print large runs at lower cost

Offset Printing Process

Offset steps: pre-pressBefore the job can be printed offset, your document must be converted to plates. The plates are created from the digital file. Each of the ink colors - black, cyan, magenta, and yellow - has a separate plate.

Plates may be aluminium or paper.

The printing plate

Before treatment

After treatment

Mixing ink

Print colour

Print color is created by mixing halftone percentages of process (CMYK) colors.

C80%/M20% C60%/M40% C40%/M60% C20%/M80%

Print density

Print density (darkness) is created by increasing the inked area(halftone percentage)

Black 20% Black 40% Black 60% Black 80%

Screening

One half-tone image may contain thousands of different shades………

Examples of screening methodsStaccato 25µm Conventional 60 l/cm

Paper Size Issues

• Print publication (book/magazine/newspaper/ newsletter)formats are based on standard flat sheet paper size, folded, bound, or saddle-stitched.

• Examples:• 11 x 17 sheet double-fold (either 4 or 8 page newsletter)• 8 ½ x 11 magazine in signatures (groups of 8 pages)

• Decisions made about format affect cost • Printers create in signatures of 8 pages or a codex of

16. So you must work in multiples of 4!

2nd step: press runSheet paper is fed through the press. The image area of the plate picks up ink from the ink rollers. The water rollers keep the ink off of the non-image areas of the plate. Each plate transfers its image to a rubber blanket that in turn transfers the image to the paper. The plate itself does not actually touch the paper - thus the term "offset" lithography. All of this occurs at an extremely high speed.

A typical Heidelberg press can run at 15,000 impressions an hour.

Chill rolls

Specialty printers for various types of jobs introduce unique technologies Here, chill rolls cools down a web press run and solidify the ink binder Steel cylinders (3 - 6) with cold water are pumped through

Print definition depends on paper quality

Coated Fine,70l/cm

SC,54l/cm

LWC,60l/cm

Newsprint,48l/cm

After the 4 printing set-ups

3rd step: finishingWhen presses have finished the printing process:Papers are trimmed to the final size using guillotines.The cut papers can be• left as they are for flyers, leaflets• collated and folded for folded leaflets• bound, stitched and laminated for books and booklets.

Shown—pro collator

Post-press

BinderyBooklets may be…

– perfect bound (glued)—above 100 pages

– Saddle stitched (stapled/sewn) typically less than 100 pages

Mechanicals• Digital files prepared using industry-standard software, and including

all links, photographs and/or illustrations, font folders and image folders. (Often, an InDesign, Photoshop, Illustrator file, final JPG, or a PDF.) Also called digital prepress files.

• It is important to keep in mind that what may be an easy trial and error process for printing at home becomes a costly transaction once it moves outside of your control to other working professionals.

• For this reasons, further study should include not only mastery of the specific program you have chosen to work with but also more detailed information concerning prepress preparation and printing technologies.

Bleeds, etc.Bleed--a printing term referring to type or a visual that extends off the edges of the page. To allow for deviations in trimming the document after printing an element that bleeds is extended about 1/8 inch or 1 pica beyond the trim lines (page edge). A bleed is set up with printers marks.

Printers Marks

B. Registration markC. Page information

D. Trim marksE. Color bar

F. Tint bar

Designing Art for a Bleed• The important thing when working in Photoshop with a photo

that will bleed off a document page is to remember not to crop the photo so close that losing a ½ inch all around will ruin your image. Leave lots of active margin space and do your cropping in InDesign.

DefinitionsPackaging—Going into the FILE menu in InDesign, Photoshop, and Illustrator to create a folder to store all your links, fonts, and original images used so they can be installed on computers where other folks are opening your file. Rich black—A combination of colors preferred by professional printers for greater richness and darker tone in depicting solid black. Rich black is typically made up of 100 percent black, 60 percent cyan, 40 percent magenta, and 40 percent yellow. Reverse type—White type. In printing, reverse type appears white by “reversing out of” the ink to the paper—in other words, containing no ink and thereby appearing white.

Definitions“Rich Black”In printing, there are many different types of black you can use (RGB, Photoshop, neutral rich, registration, flat, designer, etc.) Printers refer often to “rich black” which is not 100 percent black but includes some other colors in it for richness (typically 100K, 60C, 40M, 40 Y).

This is an ink mixture of solid black over the other CMYK color that results in a darker tone than black ink alone generates in the printing process. You can choose rich black in your Adobe programs. However, if you need small text knocked-out of a black background, make sure that it doesn’t include these amounts of cyan, magenta and yellow. If you do, the text will print blurred. This will happen because of ink-bleed and possible slight misalignment of printing plates. For best results here, use white text on a background that only has black in it.

Prepress IssuesPREPARING MECHANICALS FOR PRINT• Files destined for print should be set to 300dpi. DPI stands for

Dots Per Inch.• As designer Franz Jeitz advises: "When it comes to printing,

especially large format printing, vectors are your friend. Try to design as much as possible in a vector based program such as Adobe Illustrator. Not only will it reduce your file size, but it will ensure that you get the crispest print result.”

• CMYK (Cyan-Magenta-Yellow-Black color process) is used for print materials. Check your color modes.

• Run a pre-print check. In InDesign this is known as a “Pre-flight” and it will bring up any issues such as RGB files being used or fonts used that aren’t embedded.

Prepress IssuesPACKAGINGIn InDesign, Photoshop, and Illustrator, packaging means you create a folder to store all your links, fonts, and original images used to be installed on computers where other folks are opening your file. The command for creating this folder is in the program’s FILE menu.

Formatting InDesign documents for press--(Oft overlooked formatting requirements)

1. Any black and white images should be converted to grayscale. Otherwise, cyan, magenta and yellow inks will be added when your image when printed. Particularly important if your printer plans to use only black ink on some pages.

2. InDesign files sent to offset press should use only JPG photos. Gif and png files are on-screen-only file formats not intended for print and will not print well. (Gif and pngs are 72 ppi and images for print need to be in the 300-400 dpi range.)

Formatting InDesign documents for press--

3. Flatten your layers. If you fail to flatten layers before you export to PDF your file will be huge. Your artwork should still print okay, but it will bloat your file size and may send your printers’ Macs into meltdown.