Having a basic understanding of the concept of colour in print and the difference between colour used for digital media is essential before starting any design process, especially when it comes to print. The absolute best way to fully grasp the printing process would be to go visit a printing factory. Printers and the printing processes have progressively changed over the years. There are 5 common printing processes, Digital, Litho or Offset Litho (Lithography), Flexo (Flexography), Gravure and Screen Printing.
In my experience the most common of these would be digital printing and offset printing otherwise knows as litho. Although I used to have to prepare files for screen printing quite often in the past, I can honestly say that I’ve not had to do that for many years, but ultimately it would depend on what you’re printing. Today printing machines can convert print files to CMYK if not already prepared correctly, but remember the end product may result in colours being mixed differently (with different % breakdowns) so the final print may differ ever so slightly. To ensure the best and most accurate outcome you should always create your artwork in the correct colour mode or with the correct colour palette and if you’re creating something for print, you always need to be using CMYK during the design process.
So what is CMYK really? CMYK… as we all know it’s the colours Cyan, Magenta, Yellow and Black. It’s the colour model of the four process colours, a subtractive colour model to be more specific. So what does the K really stand for? You guessed it... it stands for Key… it’s the key plate that prints the detail.
Have you ever prepared a file for print and gone into the PDF to view the colour separations? If not, I highly recommend it. These colour separation views are great for helping to understand the print process. For litho printing especially as this shows you how each printing plates will be made up. It shows how the positives of each colour are layered to create the final print.
In Acrobat go to: Tools / Print Production / Output Preview
Deselect one colour plate at a time until none are left and then layer them back. That’s ultimately how the ink will be layered to achieve the final product.
Images and CMYK
When it comes to images though it is not entirely necessary to convert colours to CMYK as the awesome technology we have today has meant print work flows do a great job of converting RGB to CMYK. It’s always advisable check with the printer first if you don’t intend on saving the linked images as CMYK. Should you convert the images to CMYK perhaps wait till the end of the design process to do so, as the reality is RGB files sizes are substantially smaller than CMYK files – so it it’s a big time saver on processing time – depending on the speed of your computer and how much RAM you have. On a side note, I am really old school always import my images as CMYK for any and all print material, I feel more organised in this process and will constantly be checking for errors during the production.
How many designers out there have exported a large file to pdf and the error message failed to create pdf pops up? It’s the most frustrating error message, and I will cover my fixes I have found for that error at a later stage, but ensuring there are no obvious errors in the design process helps a great deal for overcoming any of those gremlins that may creep in at a later stage.
Next time I write about colour we’ll look at the ‘fifth colour’… Pantone colours. Meanwhile, I recommend saving an image as CMYK and RGB and seeing the difference in file size, and then prepare a pdf print file and go have a look at the colour separations in Acrobat.
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