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CMYK vs RGB???

Posted by Adrian Davis on

When creating a design for print, there are many different things you’ll need to consider. You need to think about the layout, the stock (type of paper) it will be printed on, any extra finishing that will be involved (creasing, forme cut, lamination, etc). All of these different things can feel a bit like walking through a minefield to the novice but that’s where an experienced printer can be worth their weight in gold. Unlike many other printers, at Saxon Print we’ll take your precious artwork and physically look at it before going to print and advise on any alterations or tweaks which may be necessary to get your project to the high standard you expect and deserve. We don’t rely on fully automated processes that can miss some obvious mistakes. Over the next couple of months we will be publishing a series of blogs explaining different aspects of printing that you may need to consider to get the best out of your design.

This week at Saxon Print we are starting off with the difference between RGB and CMYK colour modes. ‘What’s a colour mode?’ I hear you cry, do not fear I will explain.

When designing something for the internet, you don't really need to worry about colour modes as the majority of colours will appear fairly similar on most monitors. They are all capable of displaying a range of colours in the RGB colour mode. This said, it would be incorrect to assume that when designing a job for print, the colours you see on the screen when creating your design will remain the same when printed CMYK. A designer getting this wrong can lead to a very unhappy client. But what exactly does RGB and CMYK mean and when should you be using these various colour modes? Well, we don't want to see you make the common mistakes that many designers have, so we've created a guide to the differences between RGB and CMYK below.

So let’s start at the beginning...

What is RGB?

RGB, which stands for Red, Green and Blue is an additive colour model. This means that a combination of red, green and blue light is added to create a broad array of colours, eventually ending up with white. For example if you want to make yellow you add green and red light, mixed together you will get yellow. If you want to make a light blue you add green and blue (this may seem counter intuitive but trust me I’m a printer).

The reason for RGB being the standard colour mode for most applications is that it offers a wide selection of colours. By combining primary colours (Red, Green and Blue) in differing amounts, you can achieve almost any colour you like with great accuracy. The majority of photo editing and desktop publishing programs will use RGB as standard (including Microsoft Publisher and Adobe Photoshop) which is why you will need to be extra careful when designing for print.

What is CMYK?

CMYK stands for Cyan, Magenta, Yellow and Key (which means black, we’ll call it black to save any confusion). CMYK works in a different way to RGB. CMYK is a subtractive colour model, this means that when combinations of Cyan, Magenta, Yellow and Black inks are added together to create colours, you will eventually end up with black subtracting the light. For example, if we add cyan and yellow together (or if you want to be precise subtract yellow from cyan), you end up with the colour green. Again if we were to subtract yellow and magenta, you would end up with the colour red.

Plainly, this works in a totally different way to RGB as the colour combinations are essentially opposite, in addition, CMYK works with an extra fourth colour rather than the three that RGB uses. The reason the CMYK process works is that as you combine the colours together, the light is absorbed (or subtracted) to create the different various colours. For example, if we add cyan, magenta and yellow together in equal quantity (say 80% of each), we create a dark brown colour. It's only when you add black (Key) that the full amount of colour (light) is completely subtracted from the image.

CMYK isn't used as the default on many home software packages as many home printers are actually able to print using the full RGB spectrum. Nevertheless, CMYK is used by professional printing companies so if you're looking to get something printed professionally and you want the colour printed to match your design, you will need to be aware of this.

An Example

If you take a look at the image, you'll see how RGB and CMYK can differ. One of the most noticeable differences between the two colour modes is the way that they reproduce the colour blue. You'll notice the main blue colour looks different on each image, this is due to the colour mode used.

Typically, blues will look more vibrant when presented in RGB compared with CMYK. This means that if you create your design in RGB and print it in CMYK (remember, professional printers use CMYK), you'll see a beautiful bright blue colour on your screen but on the printed version, it will appear flatter and closer to a purplish blue.

The same can be applied to greens and oranges, they tend to look a little flat when converted to CMYK from RGB. Brighter colours can be the worst for this.

When Should You Use RGB or CMYK?

This is a common question that we are often asked. Truthfully, it depends what you're designing and what the final intended use will be (e.g. print or digital). If you're designing for publishing on the internet then you'll want to use the RGB colour mode. But If your design will also be used for a printed product there are times when you will want to use the CMYK colour mode.

Most of the time you can work in RGB and convert your project to CMYK near the end of the design process, checking that the conversion to CMYK is acceptable before you send it off to print. By working this way round you'll be able to create your design with the full RGB gamut, giving you smaller files and more colour freedom.

However, there are times when you should use the CMYK colour mode from the beginning of the design process. If your design is mostly grey in colour (not completely), then you might want to consider designing in CMYK. The reason for this is that in RGB, grey is created using red, green and blue (in mostly equal quantities). In CMYK on the other hand, it will be printed using cyan, yellow, magenta and black. When printing, grey can be one of the hardest colours to properly control. If you use RGB and convert to CMYK later the final printed version of your chosen colour often gives results looking rather pink. However, when using CMYK colour model, you have black (the Key colour) which can be used to control the process and ensure that grey is printed as it should be.

In some cases, you don't even need to convert from RGB to CMYK before the final printing process. It will depend on the complexity of your design, the colours you're using, and the type of print process used. 

To Wrap up...

Basically, designing for print can be a quite straightforward process. As long as you are conscious of the differences between RGB and CMYK and aware of the potential colour variations between what is displayed on screen in RGB and produced when printed in CMYK, you'll be able to ensure that you take the necessary steps to avoid expensive mistakes.

Remember if you've created your designs in RGB, you’ll need to remember to convert the design to CMYK before sending it off to print. You may also need to manually correct some colours in your design by adjusting the cyan, magenta, yellow and black (Key) values, to bring them closer to their original colour.

If you intend to produce designs for printed media (e.g. flyers business cards, etc), the best option might be to use programmes such as Adobe Illustrator, CorelDraw or a similar vector-based application; just remember to use CMYK. Either way, it's always wise to print a hard copy off before you send it to us to check for colour and layout. If you have any concerns about colour accuracy, layout etc. it’s always best to talk to us before starting the printing process. We offer a File Assist & Print Service, for a small fee, we can produce hard copy proofs, give advice and alter the files for you. It can save you the trouble of your print jobs not looking the way you hoped they would, not to mention the hundreds (or perhaps even thousands) of pounds lost to re-printing costs.

If you to want confuse yourself and learn at bit more about colour theory here is a good place to start.

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