The Prepress Toolkit - Understanding Printed Image

The Prepress Toolkit Understanding Printed Image

Aaron Trigg

Overview Before diving in to any project it is wise to consider what it will take to get your project produced smoothly. There are many unforeseen factors that can ultimately crush your chances of having a flawless project. The Prepress Toolkit handbooks are designed to get you, the designer, through the prepress process with your sanity intact. Use these handbooks as quick reference guides to keep with you when starting in on a project and let them guide you through till the end. Follow us down the rabbit hole.

Aaron Trigg

Using Spot Colors Spot, not just the name of your dog anymore.

Spot color uses customized inks that create very specific results when they are applied to paper.

Pantone is the most common spot color system currently in use in North America and Europe, but other systems such as FOCOLTONE and TOYO exist as well. When a specific Pantone color is used in a document, the print shop mixes it from a predetermined formula before applying it on the press.

Why use spot color? The main reason for using a spot color is to have accurate color unlike CMYK where is always a crap shoot. Economics is also a big reason. It allows a designer to strategically utilize color without the expense of running a The Prepress Toolkit

job on a four-color press. Black and a chosen spot color (or even a spot color on its own) can be used to add an element of eye-catching color without breaking the budget.

In the world of desktop publishing, the differences between spot color and CMYK lead to a number of traps waiting for the inexperienced designer. A big one is mixing the two in a document. While corporate designers with big budgets will often mix a spot color with CMYK to achieve a certain effect (metallic and fluorescent spot colors added to a CMYK mix are prime example), doing so unintentionally is a recipe for disaster. If the job is a four color job and a Pantone is inadvertently

inserted into the mix, one of two things will happen. The first option is that a fifth plate will be created by the printer, who will then run the job through the press to add the additional Pantone color, resulting in unexpected expenses. The second option is that the Pantone plate will be left out entirely, which will probably result in missing text or graphics in the printed product.

On the other side of the spectrum, if a job designed to be spot color is created using CMYK instead, four plates will be created to simulate the spot color, instead of a single plate. The result will be budget headaches and printing delays.

An added problem is that most design software is very picky in how it deals with the naming of spot colors. While you may think that Pantone 123C is the same as PANTONE 123c, the software will disagree. Because of the differences in capitalization, they will be seen as two different spot colors, and two different plates will be generated (resulting in more budget overruns). All of which makes the difference between spot color and process color not just a design factor, but a dollars and cents factor as well.

Applying Spot Color Single Color TIFF

This is the simplest of all the spot color options. It is a raster image saved out as a greyscale image.

Black is considered the one color within the image. The only way you can change the color of this type of TIFF is if you bring it into Indesign, select the image using the direct select tool and applying your spot color. Beyond that there is no way to adjust the images color. Use a Spot Color TIFF if you would like to to customize your colors a little more.

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Spot Channel TIFF

Spot channel TIFF are an extremely useful format because they are the lovely TIFF format we all love and you do not have to deal with the headaches of EPS. You are able to store the spot color information directily in the file by adding them to the channels pallet in Photoshop.

The catch with this format is you have to use a grey channel along with the other channels you choose. If you do not need a grey channel you may consider using a Multi-channel EPS for you desired format.

Spot Channel TIFF

Single Color TIFF

Single Color TIFF

Duotones

Duotones are two-color halftone image reproductions. Typically, a duotone will be made up of black and one other color. When creating a duotone print, the two colors should used at different intensities. Doing so will create an image with more subtle coloring the integrity of the image will be maintained. If done correctly, the result is a photograph with greater depth of color than a plain, grayscale photo.

Dougraphs

Duographs, or “fake duotones,” are created by printing a one-color halftone over a tint or solid color. The effect is not nearly as effective as a true duotone print and the image loses a great deal of clarity and detail.

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Multichannel EPS (DCS)

This is the most versatile of all the spot color formats availably. DCS stands for Desktop Color Separations. It’s an EPS file format for Photoshop that allows you to save color separation information for either CMYK or as many spot colors as you wish. Usually you use DCS 2.0 to export spot color information. The color separations are editable just like any other layer within Photoshop allowing you to place the colors where ever you need in any order. The beauty of this format is you do not need a grey channel unlike a spot channel TIFF. Be sure that the color mode is set to multichannel.

Multichannel EPS

Dougraph TIFF

Duotone EPS

The Halftone The great image Houdini; creating the illusion of continuous tone.

Knowing about density values, halftone screens and laser scanning can help you achieve high quality print reproduction. If the printer’s only concern was to reproduce type, his trade would not be nearly as difficult, challenging nor as interesting. The basis of fine printing is in the reproduction of photographs, either in full-color or in black-and-white. Much is written about the four-color process and color separations, but very little is devoted to the black-and-white photographic reproduction known as halftone reproduction.

In its most basic sense, a halftone reproduction is actually only a facsimile, made up of small, The Prepress Toolkit

regulated dots in a predesignated grid pattern.

Our eyes take in the dots and blends them in the mind’s eye into a smooth photograph. If you look through a magnifier (loupe) at any printed photograph, you will notice that it is indeed made up of these small dots. But why can’t a photograph be printed on the paper as we see it and why is the halftone process necessary, novice print buyers or artists might ask? Because printing is an all-or-nothing process-either the press puts down an even coat of ink on the paper or it does not. Printing presses cannot differentiate tonalities or densities of black into the shades of grays we see in photographs. With the halftone process, however, the dot pattern

400% Image: round halftone pattern

and the size of the dot itself and its immediate surrounding white space can be controlled. While looking at a halftone through a magnifier, notice that the bright (highlight) areas are small black dots surrounded by a lot of white (paper). In the middle gray range (midtone), the dots are in the same position on the grid but have increased in diameter with less white surrounding. Finally, in the shadow areas the dots are very large (in most cases overlapping) with very small white areas between. By being able to control the size and placement of the dots, a full tonal range from white through the gray scale to solid black can be achieved, overcoming the ink/no ink limitation of the press.

400% Halftone Shapes They come in all different shapes and sizes. That’s what she said.

There are many halftone dot shapes available: round, square and elliptical are some of the more common but also available are diamond, cross and line and many other specialty shapes. Each is used for different types of presses or for special types of subject matters.

Round Dots

Round dots (found on page 5) are best suited for high-speed web offset printing because the uniform round shape extends the midtone range while minimizing highlight and midtone dot gain.

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Square Dots

Square dots, also known as conventional dot screens, are used with letterpresses, sheet and webfed offset. Square dots are unusual in that the dots are square-shaped in the midtones yet are round in shape in the highlight and shadow areas. The symmetrical square shape minimizes the density variations due to the directional effects and shimmy of the presses.

400%

400%

Eliptical Dots

Halftone Lines

The elliptical dots, also called chain dots, offers a very smooth gradation in the midtones and is ideal for portraits or other halftones where the emphasis is in the midtones.

Photoshop is capable of creating some very interesting halftone shapes that break out of the traditional halftone dots. They are usually used for artisitc purposes. McDonalds is known for using halftone lines to make people on their cups seem slimmer.

Halftone Line Screens (LPI) The more there are the less you can see them. Details people.

The number of dots to the inch or the line screen used will determine how closely the halftone resembles the original continuous tone photograph. The untrained human eye no longer recognizes a dot pattern once it exceeds 120-133 lines to the inch. Very fine brochures, annual reports, magazines and art prints use line screens of 150-200 or even 300 lines (the tightest commercially available screen) to the inch. The idea is to print the smallest dot pattern possible so that the eye cannot perceive the dots at all, and thus will mistake the printed halftone for the original photograph.

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The line screen used is determined primarily by two factors: the paper it is to be printed on and the printing press to be used. Uncoated, rough stocks such as newsprint and inexpensive offset papers are very absorbent. This absorbency causes the dot of ink to spread, called dot gain, it greatly distorting the actual value of the dots.

This increase shifts the halftone toward the darker (larger dot) scale. Finer, smoother grades of paper and coated stocks have better ink holdout so that the dot is not absorbed by the stock and the dot retains its shape with little dot gain.

150 LPI

85 LPI

55 LPI

35 LPI

Lines Per Inch

Printing Techniques Choosing the right tool for the job shouldn’t be rocket science.

When you are going to produce a printed product you must choose the technique that fits best, keeping in mind certain prevailing conditions. What mainly affects the choice of technique is layout, format, size (number of pages), quality requirements and what material you are printing on. Be sure to use the appropriate printing technique for the job. It is always wise to plan ahead and design for the type of print job and not the other way around.

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Planographic Offset Sheet & Web Fed

This type of printing is extremely economical and popular. Set up time is limited and mass production of newspapers, magazines and flyers is quicker and faster. Here the text and images are transferred first on to metal plates and then onto rubber cylinders. The printing process begins and rubber cylinders offset the text onto the paper. It is also called lithography.

Image Carrier: Print Runs: Format: DPI/ LPI: Print Carrier: Format: Pros/ Cons:

Plate 500 - 1,000,000 A3 Up to 200LPI Paper, Cardboard Sheet, Roll High quality

Waterless Offset

Waterless Offset is a printing method where the inked areas are higher than the non-printing areas which are pitted out. The inked areas are therefore placed in contact with a rubber surface which in turn transfers the ink to the material to be printed. This process eliminates the use of water as required in the conventional offset lithographic printing process.

Image Carrier: Print Runs: Format: DPI/ LPI: Print Carrier: Format: Pros/ Cons:

Plate 500 - 50,000 A3 Up to 200LPI Paper, Cardboard Sheet, Roll High quality, Waterless

Offset Thermography

Commonly known as poor man’s engraving, thermography produces raised printing similiar in appearance to engraving but using a different process. In thermography, a special powder is added to the ink printed on the paper. The printed piece is heated and the powder and ink mixture dries to form a raised effect on the paper.

Image Carrier: Print Runs: Format: DPI/ LPI: Print Carrier: Format: Pros/ Cons:

Plate 500 - 50,000 A3 Up to 200LPI Paper, Cardboard Sheet, Roll High quality, Raised

Relief Flexography

Flex is a special surface which is thicker than paper. The composition is different as well.

Flex is used for signages as too. Flexography is the printing process on this flex surface. This technique is also used for printing labels and other matter on bottles and cardboard boxes.

Image Carrier: Print Runs: Format: DPI/ LPI: Print Carrier: Carrier Format: Pros/ Cons: The Prepress Toolkit

Flexographic forms 50 + N/A Up to 150LPI Plastic Flat for even forms Can’t show light tones

Letterpress

Gutenberg’s brainchild, this is considered to be the original printing method. It has become obsolete but worth a mention because it paved the way for relief printing. In relief printing the image or text that needs to be printed is raised from the core surface.

Image Carrier: Print Runs: Format: DPI/ LPI: Print Carrier: Carrier Format: Pros/ Cons:

Stamp-like from 50 - 500 A3 No rasters Paper Sheet Creates a relief imprint

Foil Stamping

Foil stamping is the application of foil, a special film-backed material, to paper where a heated die is stamped onto the foil, making it adhere to the surface leaving the design of the die on the paper. Foil stamping can be combined with embossing to create a more striking 3D image.

Image Carrier: Print Runs: Format: DPI/ LPI: Print Carrier: Carrier Format: Pros/ Cons:

Stamp-like from 50 - 500 A3 No rasters Paper Sheet Creates a relief imprint

Embossing

The creation of a three-dimensional design or image on paper is known as embossing .

Heat and pressures reshapes the surface of the paper to create the image. Single, multilevel, beveled, and sculptured are the styles of embossing. Embossing can be done on plain paper or combined with ink, images, or foil for special effects.

Image Carrier: Print Runs: Format: DPI/ LPI: Print Carrier: Carrier Format: Pros/ Cons:

Stamp-like from 50 - 500 N/A N/A Paper Sheet Stretch paper

Intaglio Gravure

With gravure printing an image is etched on the surface of a metal plate, the etched area is filled with ink, then the plate is rotated on a cylinder that transfers the image to the paper or other material.

Image Carrier: Print Runs: Format: DPI/ LPI: Print Carrier: Carrier Format: Pros/ Cons: The Prepress Toolkit

Engraved cylinder 100,000 + N/A Up to 200LPI Special engraving paper Roll Raster objects and text

Engraving

In engraving, a metal die with an impression cut into the surface is filled with an opaque engraving ink then pressed against paper creating raised areas of the paper coated with ink. Engraving creates the raised surface on the front of the paper.

Image Carrier: Die Print Runs: 50 - 500 Format: N/A DPI/ LPI: Up to 150LPI Print Carrier: Paper Carrier Format: Flat for even forms Pros/ Cons: Raised surface without impression

Image: Offset printing press

Stencil Silkscreen

Silkscreen primarily uses stencil. The part that is to be printed is made up of silk, nylon or a stainlesssteel mesh. Ink can pass through this area but not through the other part of the stencil which is contained inside a frame. The printing surface is placed under the frame on a flat surface. The impression is made by forcing the ink through the screen area with a rubber squeegee.

Image Carrier: Screen Cloth Print Runs: 100 - 200 Format: N/A DPI/ LPI: Up to 100LPI Print Carrier: Cloth, paper, metal, plastic, glass Carrier Format: Flat and cylinrical forms Pros/ Cons: Can’t show light tones

Digital Printing Who knew that ones and zeros could be so darn useful?

It’s the digital age so, naturally, we must include digital printing as well! It is quickly replacing offset printing as the most preferred printing process as it is quick and cost effective. Some believe that the quality of digital printing is not as good as offset but with newer machines and designing software it’s all changing. Think of digital printing like a copy. You need plates, films or cylinders for offset printing. In digital printing the material that’s needed to be printed is accessed directly from the computer and printed like a copy.

Print On Demand

Print on demand (POD) refers to digital printing The Prepress Toolkit

technology that allows one or two copies of a book to be printed at a time, dispensing with the expense of warehousing books. It also allows a publisher or author to have books printed only as they are ordered, which means that at the end of the year, a publisher doesn’t face costly returns from bookstores. In recent years the quality of print-on-demand books has improved to the point that there often is little difference between them and the average traditional print book.

Variable Data Printing

Variable data printing uses digital printing technology that customizes communication by linking databases that contain the content

Image: Xerography printing.

for printed documents to a print device, such as the copier. The customized communication includes rules that specify the selection of content from the database and the placement of that content in the document.

Variable data printing is typically used for personalized mailings, such as direct-mail advertising. It involves combining a set of master elements that are common across copies of a document (reusable data) with a set of variable elements that change from copy to copy. When you use variable data printing, you create personalized communications with elements that have special appeal to your targeted audience.

Digital Print Tech Xerography

A dry photographic or photocopying process in which a negative image formed by a resinous powder on an electrically charged plate is electrically transferred to and thermally fixed as positive on a paper or other copying surface.

Image Carrier: Print Runs: Format: DPI/ LPI: Print Carrier: Carrier Format: Variable Data: Pros/ Cons: The Prepress Toolkit

None 1 - 1,000 A4 - A3 Up to 1200DPI Paper, Overhead film Sheet, roll Parts of pages can vary Limited quality

InkJet

Typically, inkjet printing forms images by spraying tiny droplets of liquid ink onto paper.

Small size and precision placement of the dots of ink produce very near photo-quality images. Two primary inkjet technologies are thermal bubble or bubble jet and piezoelectric.

Image Carrier: Print Runs: Format: DPI/ LPI: Print Carrier: Carrier Format: Variable Data: Pros/ Cons:

None 1 - 20 A4 + Up to 9600DPI Paper, textile, plastic Sheet, roll Prints out page by page Large tonal range

Image: Passport photos are printed using Dye Sublimation.

Dye Sublimation

Dye-Sublimation uses high heat and solid dyes to produce photo lab-quality images. Dye-Sub printers contain a roll of transparent film made up of page-sized panels of color. Solid dyes in cyan, magenta, yellow, and black are embedded in the film. Print head heating elements vaporize the inks which adhere to a specially-coated paper.

As the ink cools it re-solidifies on the paper. This technique is the only printing process that can recreate continuous tone images.

Image Carrier: Print Runs: Format: DPI/ LPI: Print Carrier: Carrier Format: Variable Data: Pros/ Cons:

None 1-5 A4 - A2 Up to 2400DPI Paper, plastic, shrink wrap Sheet, Prints out page by page Large tonal range

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The Prepress Toolkit Understanding Printed Image Aaron Trigg