CMYK & RGB Explained

Wednesday 2nd February 2011

Full Colour

Full colour (also known as four color) printing is the process of using four specific ink colours (Cyan, Magenta, Yellow and Black) and mixing them to create the colour you desire. Very much like mixing paint!

Mixing Cyan and Magenta will give you Blue. Different percentages of Cyan and Magenta will give you various shades of Blue. Add in some Yellow and Black and you can create almost any colour you like.

These four colours however are limited to a spectrum and certain colours will not be as vibrant as you may desire. Orange for example when created using CMYK will produce only a dull orange which next to certain colours may sometimes look brownish. As a note K is used to specify Black as not to get confused with B which could stand for Blue in some setups.

Spot Colours

Obviously using four colours will cost more to print than using one or two and so in some circumstances it's better to print using only two colours. These two colours don't have to be CMY or K they can be any colour you choose and that your printer has access to. They can be chosen from swatches much like paint at your local DIY store. The most widely used system is from a company called Pantone®, they produce thousands of specific colours which can be chosen from swatch books they produce. Most industry standard graphic design packages like Illustrator, InDesign, QuarkXPress and Photoshop have these swatches already built into them so it's simply a case of looking at your swatch book, choosing a colour you like and selecting it in your colour palette within your chosen graphics program. These specific colours go by many names such as Spot, Special and Pantone (if from the the Pantone system).

The main benefit of these spot colours is the fact that if you want an exact colour match you can pick it from a book and know that is what you will get once printed. Using CMYK inks there is often a colour shift as it is hard to match what is on screen to what is actually printed. This all comes down to screen calibration and will be covered in future article. The second benefit of using spot colours is the cost. To create a Blue using CMYK would require using C&M i.e. two inks. If you choose a Blue spot colour instead then that cuts out the need for a second colour to mix the Blue.

The main drawback of spot colours is that you are limited to the spot colours you choose. i.e. its not advisable to mix spot colours to create a new colour as the results are often hit and miss. If you choose Red and Blue everything has to consist of Red or Blue and tints there of.

Getting back to the cost of printing only two colours instead of four. Obviously the overheads like number of inks and printing time will work out less but many professional printers will be set up to print CMYK by default and may actually charge a bit extra to print spot colours if they need to clean the CMYK inks off the machine and replace them with your chosen spot colours. So the reduced cost benefit of printing spots instead of CMYK is usually negligible. If the printer is a large company and has large print machines that can print more than four colours at once then it may not matter too much. On the flip side some small print firms may only have a single colour machine and for every ink used the machine will need to be cleaned and set up again to run the next colour adding time to the job and possibly cost to your bill. It's very worth while getting to know your local printers, their set ups and preferences so you can better judge which job will fit which printer best. This helps keep costs down for you and the printers will appreciate you that bit more because you will know not to send a CMYK job with additional spot colours to a print firm with a single colour machine.

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