Page 149 - Graphic Design and Print Production Fundamentals

Graphic Design 137
to the substrate independently. Process inks are only the four primary colours: cyan, magenta, yellow,
and black. Process inks are transparent and are intended to be combined by halftone screening different
percentages on a substrate to render any colour in the Pantone library. Spot colour inks are more
opaque and are intended to be applied to a substrate one at a time, through distinctly separate printing
units. Since most colour photography is colour separated to render the photo in only the four primary
process inks, most documents are created intending to convert the spot colours to process colours. They
can be imaged with the photographs in the document. A designer must know how many colours the
output device is capable of when deciding which colours will remain as spot colours and which will
be converted to CMYK process colours. Most inkjet and electrophotographic devices are only capable
of imaging with the four process colours. Some lithographic presses have extra printing units that can
print spot colours, so six- and eight-colour presses commonly print the four process colours and two
(or four) extra spot colours in one pass. It is not uncommon to have 10- and 12-colour flexographic
presses that image no process colours but use 12 spot colours. This is because, historically, flexo plates
cannot consistently reproduce very fine halftone dots reliably. This is changing with the development
of high-definition plating technology, so we are seeing more photographic content produced well on
flexographic presses. Flexography is primarily used in the packaging industry where spot colours are
very closely tied to brand recognition in retail outlets. A designer must be very aware of the imaging
technology used to reproduce a document when deciding which colours will remain spot colours.

This is where the next round of challenges begins when preflighting (assessing) documents for imaging
to substrates. If design elements stay as spot colours, it is a simple process to maintain the spot colour
on the output device and to image with the appropriate ink or toner. Some software will not maintain the
spot colour in a document easily in some situations. Usually, the problem comes with applying gradients
to spot colours. It is very easy to introduce a median colour value on a spot colour gradient that is
simulated with a process colour value. The screen version displays a nice smooth gradient that looks like
what the designer intended to create. When imaging on a substrate, the gradient will have to be broken
down into individual colours: from the solid spot colour to a value of CMYK and back to spot colour. It
is very hard to recognize this by viewing the document, or even a composite PDF file. Viewing separated
PDF files, or using a ‘separations’ tool in Acrobat, will show the problem before it gets to a printing
plate.

There are also colour problems associated with nested files generated in different software. For example,
if we create a magazine page with a headline colour named “PMS 123,” add a logo created in Adobe
Illustrator with type in a colour named “Pantone 123,” and insert a PDF ad created in Apple’s Pages
layout with a border specifying “PANTONE 123,” then even though they are all the same, colour-
separating software will generate three separate spot colour plates for that page. The spot colours
have to be named exactly the same and come from the same library. Some modern workflows include
aliasing rules that will match numbered PMS colours to try to alleviate the problem. Colour libraries
can be a problem as well, especially if our software allows the library to convert the spot colour to a
process colour. The same colour library in two different versions of Adobe’s Creative Suite software
can generate a different process colour recipe for the same Pantone colour. This is not a problem if all
the document elements are created within one software package and all spot colours are converted to
process colours. The problem arises when a designer places a graphic file from other software on a page
with the same colour elements. A logo created in an older version of Adobe Illustrator will use that
colour library to look up process colour recipes that can be very different from the recipes in a recent
colour library used in Adobe’s InDesign software. So all the Pantone orange colours in a document are
supposed to look the same, but do not because the spot colour to process colour conversion has not been