This article explains the difference between the RGB and CMYK colour spectrums. With this text we hope to explain to you the reason CMYK should always be used when commercially printing your documents. While also showing you the best way to check your colour settings on the most common software.

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1. Colour Gamat differences

RGB graphics are made up from Red, Green and Blue while CMYK is made up of Cyan, Magenta, Yellow and Black.

 

CMYK colours are subtractive meaning the starting canvas is white and colours are added to block out parts of the spectrum RGB colours
are additive meaning that the starting point is a black canvas (i.e. a computer screen) and colours are added to create the final image.

Why do print files need to be CMYK?
Since the RGB spectrum is broader than the CMYK spectrum, there are many RGB colours that cannot be recreated as CMYK. This becomes more noticeable when using bright, fluorescent colours such as green, yellow or orange. Therefore all artworks should be designed with this in mind, as all commercial printers print in CMYK colours in order to get the best results. This means there is no point in using colours that won’t print correct. Below are files that have been created using RGB colours and how they look when converted to CMYK.

Creating the files in CMYK, or converting the files before sending them to print, will avoid any colour change surprises upon receiving your leaflets.

2. Converting RGB files to CMYK and re-balancing colour

It is possible to readjust the colour balance when using photoshop. This means that after converting your images to CMYK, you are able to adjust the colours back to how they originally looked. If you are using RGB images within your design it would be best to readjust the colours as you go along.

 

RGB – Original image to be used. (Notice the vibrancy of the blues)
CMYK – Colours are converted straight to CMYK, see gree backgorund has become dull
Re-Balanced – Colour levels are adjusted using photoshop, greens are not a vibrant as the original rgb, but brighter than tghe cmyk auto conversion

3. Creating Files in CMYK?

It is important to make sure all design files are set up as CMYK when you start. This helps eliminate any problems with converting the files afterwards as it can be a difficult, sometimes impossible, thing to do. Certain software packages are unable to create files in CMYK, such as the Microsoft Office packages. If you supply artwork in this format, we will convert it and send you a prof before we proceed. Below are guides for the following software packages.

Adobe Photoshop, Adobe InDesign, Adobe Illustrator and Microsoft Publisher – to get a larger view, simply click on the image.

Adobe Photoshop?
Colour settings in photoshop are determined when the document is created, the screen below shows the correct colour settings. You can also check colour settings when a document is open by clicking on Image, then mode as shown by the screen on the right.

When creating a document set to CMYK

Checking when document is open
 

Adobe InDesign?
With inDesign the colours are converted when the file is exported to pdf. Selecting pdf/x-1a:2001 preset will ensure that the document is CMYK.

When exporting, select pdf/x-1a2001 preset

Adobe Illustrator?

In adobe illustrator the colour mode is set when the document is created. When saving as a pdf select pdf/x-1a:2001 from the drop down presets list.

When creating the document, select CMYK colour mode.

When saving as a pdf, select pdf/x-1a2001 preset

Microsoft Publisher?
When the document is open click file – info – commercial print settings – choose colour model. This will allow you to set the colour mode that you would like the document to be set up in.

From the file menu, select ‘choose colour model’

select ‘process colours (CMYK)’

Other Software
The software shown above represents the most commonly used desktop publishing software for creating print files however documents can be created in many other packages. If using other software key settings are as follows; Colour mode CMYK (Sometimes called process colours). Colour profile: Fogra 39 (ISO 12647-2:2004). Where possible export as a PDF/x-1a:2001.

4. DOs and DON’Ts – Checking Your Files before sending

Finally, a couple of quick pointers to help you understanding the issue and assist in checking;
• DO use printed CMYK colour swatches to check colours if unsure.
• DO check proofs on screen using a colour calibrated monitor (if possible). Be aware that with uncalibrated screens colours will vary from monitor to monitor.
• DO print samples using a commercial proof printer with output profile set to Fogra39.
• DO use Acrobat pro output preview tool to check colours when output to Fogra39.
• DON’T check colours against desktop printer samples as their profiles will generally try to emulate RGB colours as opposed to printing the true CMYK colours.