For this installment of Education, we return to Pantone colour and how this can expand the printable colour range.
We all know that colour is a powerful tool for a designer. But how can you get more from colour when designing towards a print outcome? The answer may be through the use of Pantone colour. But first, let’s take a quick look at the theory of printed colour, and why CMYK and Pantone colour differs.
99% of all printed material uses a CMYK-based colour model. CMYK is based on the principle that printing varying amounts of Cyan, Magenta and Yellow, and adding Key-Black (the ‘K’ in CMYK), can produce a broad spectrum of colour. It is interesting to note that Cyan and Magenta are essentially, variations of Blue and Red—meaning; CMYK is essentially the Primary Colour set (Blue, Red, Yellow), with the addition of Black. CMYK is the colour model used for offset lithography (sometimes called ‘Process’ or ‘Offset’ printing) and for most digital print technologies. Note that whilst offset and most digital print technologies employ
the same colour model—the actual method of transferring an image onto paper is very different.
In this article, we are only discussing offset lithography. Offset lithography is by far, the most common method for large volume printing (1,000+ copies) onto paper. This method uses translucent ink; Cyan, Magenta, Yellow, and Black (the ‘process’ colours), which overprint each other in sequence on the lithographic press (see Figure 1). Note that the Black usually is printed first.
The overprinting of these four colours creates all the entire CMYK spectrum (the ‘CMYK gamut’) allowing us to print all sorts of material, including photographic images and graphics. At it most basic, overprinting these four process colours achieves all other colours (refer Figure 2).
CMYK colours are usually notated as a sequence; C=XX M=XX Y=XX K=XX, where XX is a percentage between 0% and 100% for each of the four process colours. Each percentage equates to how much ink will be printed per colour. Higher numbers result in more ink (100 is solid ink coverage). Lower numbers result in less ink (zero; means no ink).
The two examples in Figure 3, show an Orange comprising;
- no Cyan, 73% Magenta, 87% Yellow, and no Black
- and a Lilac made of 23% Cyan, 45% Magenta, and no Yellow or Black.
In theory, mixing the four process colours creates a wide printable spectrum. However, the reality is; the range of achievable colour through CMYK alone is very limited. CMYK particularly struggles to reproduce oranges, violets, sky blues, emerald greens, and deep reds. It is simply behind the capacity of CMYK to create these colours—which is where using Pantone colour comes in.
What is Pantone Colour?
Pantone (pantone.com) is an American company that develops colour systems used by many industries, including graphic design and printing. The specific system for design and printing is the Pantone Matching System (abbreviated PMS). This system comprises approximately 2,400 unique colours which are specified through a series of Pantone swatchbooks (see Pantone Swatchbooks side note). Colours are identified
using a unique PMS code—which in most instances, is expressed as the acronym PMS followed by either three or four digits to identify the individual colour, plus a C or U suffix indicating whether the colour is from the Coated or Uncoated swatchbooks (see the Coated versus Uncoated side note)—example; PMS123C.
Pantone colour in print
One key benefit of using Pantone colour—is this allows the printing of many colours beyond what CMYK can produce. In fact, over 50% of Pantone colours fall outside the CMYK Gamut. This is because, unlike CMYK, which relies on the overprinting of four process colours to create all other combinations—Pantone colours are mixed ‘off-the-press’ before printing, using a much wider wide range of base inks than Cyan, Magenta, Yellow and Black. In this manner, a Pantone colour is already the correct colour and is not dependent on overprints of CMYK to achieve the desired colour.
To illustrate the difference in printed result; Figure 4 shows our Orange and Lilac colours; on the left are the CMYK mixes, on the right are the matching Pantone colours: PMS172C and PMS529C. You can see how the Pantone versions are more pure and vibrant.
You can use Pantone colour in addition to CMYK (for example, CMYK + one or two PMS colours), or without CMYK (Pantone only). On a large multicolour lithographic press, if you run CMYK + Pantone colours, all the inks are usually printed in-line going down one after the other—see Figure 5 which shows this six-colour print job.
Just note that printing Pantone colours in addition to CMYK requires more set-up on the press and may increase print costs. Similarly, printing using one or two Pantone colours without CMYK—may slightly reduce print costs (but not always).
One method to increase the colour range when you are using Pantone is to employ overprinting—meaning to print one colour straight over another. As the printing inks are translucent, this will create a new colour. Figure 6 below shows an example of this using our Orange and Lilac to create a Red from the overprint. In fact, we used these Pantone colours on the cover of the last issue (GSM20). Figure 7 shows how
the resulting cover was achieved. Just note; The outcome of overprints when using Pantone colours can be difficult to predict. Do not rely on what you see on your Mac!
It can be an expensive mistake to find the overprints do not yield the results you expect. If overprinting is part of your design thinking, but you’re not sure what the result will be, —discuss your idea with your printer. They have years of experience with ink on paper!
Overprints can be set up in both Adobe Illustrator and InDesign. To learn how to set these up, we suggest reading the Adobe Illustrator tutorial (fundamentally, thisworks the same in both apps—but the Illustrator Help function is bit easier to filter).
In Illustrator > go to Help > Illustrator Help > keyword search ‘overprint’.
Knock-outs & Trapping
Correctly setting up artwork to use Pantone colours is really important. Get this wrong, and you may get an unexpected print result. Unless your design intentionally makes use of overprinting (see previous topic), Pantone colours should always knock-out from other spot colours plus any CMYK colours—fundamentally, this is the opposite of overprinting—the graphics using the Pantone colour will print ‘true’. Figure 8: shows an example of overprinting (A) versus knock-out (B).
Where a knock-out occurs, this should also ‘trap’ from other colours. A trap is simply a fine stroke on the Pantone shape set to overprint—the purpose of-which is to compensate for any misregistration during the printing process. Without trapping, you may end up with a fine hairline between where two knock-out shapes touch each other. Figure 9: shows an example of a knock-out without trapping (A)
versus a knock-out with trapping (B).
Adding Pantone Colours into Adobe InDesign and Illustrator
If you are a regular user of Adobe Creative Cloud—you may have noticed that since the CC2023 release, the Pantone Swatchbooks that were located in the Swatches Palette have vanished (oddly, the Metallics book is still available). This quick and easy way of adding Pantone colours into artwork has been removed due to Pantone introducing their own (paid) subscription service—Pantone Connect. However, the actual ability to use Pantone colour has not been removed—only the short-cut method using the colour books has gone.
To add a Pantone colour into either InDesign or Illustrator, follow these steps:
1. Open the Swatches palette and create a new Swatch
2. Double-click the new swatch to activate the Swatch Options dialogue box
3. In Swatch Options;
—Change the swatch name to match the Pantone colour
(e.g., PANTONE 172 C)
—Switch the Colour Type from Process > to > Spot
—Change the Colour Breakdown to match the Pantone CMYK equivalent breakdown (refer to a Pantone Colour Bridge swatchbook). It is important to note that the on-screen colour is only a placeholder and has no effect on the final printed colour. The final colour will match the specified Pantone colour regardless of what you see on-screen.
4. OK this to start using your new Pantone colour in your artwork.
Pantone Colour & Photographic Images
An important consideration when using Pantone colour is how this affects any photographic images as ‘full colour’ images are not possible without CMYK. This means if you are running a project in Pantone colour only, any photographs need to be set-up as either monotone, duotone, tritone, or even quadtone— depending on how many Pantones you are using. Figure 10 shows an image in straight CMYK (A), the same image as a monotone using PMS172 (B), and again as a duotone using both PMS172 and PMS529 (C). To learn how to set images up in this manner; in Photoshop > go to Help > Photoshop Help > keyword search ‘duotone’.
Where you are printing Pantone colour in addition to CMYK—it is possible to use PMS colours to boost the photographic images. This is called a multichannel image. Doing this successfully requires a high level of technical expertise—but it is possible and it can be used to stunning effect. Here is an example of a multichannel image set up using CMYK + PMS172 + PMS529 (a six colour image).
Hopefully, this article has provided some useful information around Pantone colour. And how this differs from CMYK process colour within lithographic printing. As a final thought; don’t let a lack of experience stop you from applying this to your work. If you are unsure about using Pantones, talk to your printer. Let their expertise help fill in some of the blanks. Most printers would rather pro-actively help you get the right result, rather than fix a mistake.
Supporting the Pantone Matching System is a range of swatchbooks. Understanding the different versions and their intended uses ensure you will use the right tool for the job:
- Formula Guide: Two x books (C & U):
Formula Guide swatchbooks show the base range of 2,400 PMS colours, along with the corresponding ink formula. Printers use these formulas to mix Pantone colours.
- Bridge Guide: Two x books (C & U):
The Bridge Guide swatchbooks show the same base range of colours as the Formula Guide—but instead of showing the ink formula, the Bridge Guides show each Pantone along with its nearest CMYK equivalent—plus provide the corresponding colour breakdowns (CMYK & RGB), and the Hexcode. The Bridge Guide swatchbooks are great tools for Graphic Designers doing colour specifying. If you are only going to own one set of swatchbooks—this is the one to have.
- Metallics Guide: One book—Coated only:
The Metallic Guide contains 600+ additional colours not featured in the Formula/Bridge guides. These all use a metallic base such as gold or silver.
- Pastels & Neons Guide: One book (C & U):
The Pastels & Neons Guide (combining Coated and Uncoated within the same book) shows 150+ pastels and 50+ neons. These are not featured in the Formula/Bridge guides.
- CMYK Colour Guide: Two x books (C & U):
See ‘Colour Gamut’ side story over page.
Coated (C) & Uncoated (U)
Most of the above swatch guides come in Coated and Uncoated versions—but what does this mean? The difference is the paper on which the swatchbook has been printed. The colours themselves are the same in
both books. Coated swatchbooks are on gloss card (Coated stock). Uncoated swatchbooks are on an Uncoated card with a more natural finish. This change in stock affects the colour’s appearance, as ink on uncoated paper appears duller and less vibrant. Hence, the two versions of each guide allow you to see this difference.
The exception is the Metallics Guide, which has no Uncoated version as these are generally printed on Coated stocks only. PMS codes end with either a C or U. These denote the colour as specified from the Coated or Uncoated guide (but the colour breakdown is the same regardless).
COLOUR GAMUT: SCREEN VERSUS PRINT
When it comes to colour, a common frustration is the mismatch between what you see on-screen versus the printed result. Understanding why this is the case, can help you to navigate this issue.
To create colour, a device screen uses varying degrees of light, specifically Red, Green, and Blue light (otherwise known as the RGB Colour Mode). More than 16 million colours are possible using RGB—significantly more than what the human eye can distinguish (about a million).
RGB vs CMYK
Compare this to the CMYK colour mode used in print, which can only produce about 16,000 distinguishable colours. Even if we add another 2,400 Pantone colours—print has a vastly reduced colour spectrum compared to RGB.
Any RGB colour which falls outside the CMYK gamut—will not reproduce accurately. Instead, you will get a ‘nearest’ approximation, which sometimes—is not a close match. To demonstrate this, if you create an Adobe Photoshop file in RGB mode and fill this with RGB Green (#00FF00)— then change the colour mode to CMYK; your green will be completely different. Photoshop has to reinterpret the RGB green into a colour CMYK can achieve—which, whilst still the same hue, is nothing like the original.
From a practical perspective, this problem manifests itself when RGB files or colours are present in print artwork—or—when a designer specifies colour from a screen without sighting a printed example of the colour. The printed colours may differ significantly from the screen versions in either situation. So, what is the workaround for this problem? Here are some suggestions:
- Firstly, understand that this is not the printers ‘fault’. RGB and CMYK are different colour models. Instead, change how you think about colour when working towards a print outcome.
- Do not use RGB Mode files or colours for print based projects, including Illustrator graphics or Photoshop images. When working towards print, use CMYK mode files and colours only.
- When specifying colours for print projects, choose these from a printed source such as the Pantone Bridge Guide or CMYK Colour Guide. The CMYK Colour guide shows thousands of CMYK breakdowns (without equivalent PMS colours). Using these tools to choose colour means the printed outcome will be very close to what you specified.
- Ask your printer to run a hard copy proof from the final artwork. A printer’s proof is the most accurate method of checking how the colours will print. If the colour on the proof is not what you expect, then you need to fix this before the project runs.