Tech Blog :: CMYK & RGB

As a CD & DVD replicator a large part of our work involves the handling of graphics and text for on-disc printing and packaging, such as DVD case covers, card wallets and Digipaks. While we offer a print design service to produce artwork files for any disc or CD / DVD packaging specification we also recognise that many of our clients want to produce these themselves. For some this means entering uncharted territory filled with incomprehensible terminology, a minefield of formats and daunting software. In this regular blog I will be attempting to illuminate the basics and provide a knowledge base for producing printed CDs, DVDs and packaging that match your vision.

Colour confusion – What are CMYK and RGB?

In order to artificially construct the varied colour tones you see in print, broadcast, and online media we need a colour system. That is, a system which takes a simple input set but has the capability of producing complexity in colour and millions of different tones. CMYK (Cyan, Magenta, Yellow, Key or Black) and RGB (Red, Green, Blue) are two such systems and the most commonly used for delivering visual information.

Which do I use?

One of the first things you might be asked when opening a new document in a graphics package is Do you want to use CMYK or RGB? The answer is actually very simple: If you are designing for print media, whether on a CD or DVD disc, DVD packaging, or 50ft poster, you will want to choose CMYK. If you are designing something to be viewed on-screen, whether computer monitor or television set via DVD-video or Blu-ray disc, or broadcast, you want to use RGB.

The reasons are, again, quite simple. CMYK is a subtractive system, which essentially means that white is the base colour (maximum reflectivity of light from the page) and increasing colour values will subtract light until you get to black. This is an ideal model for print since it mostly takes place on plain white paper or card and, for our purposes, also white-coated CDs or DVDs.

In opposition RGB is an additive system which means that the base value is black (no light) and increasing colour values adds light in order to eventually produce white. This is perfect for devices that display images by emitting varying levels of light, such as computer monitors and television screens.

RGB and CMYK objects can easily be converted from one to the other in almost any graphics package. In fact a type of conversion is happening while you produce print graphics. Monitors can’t actually display CMYK images so they show an RGB approximation while you work. We are usually able to make this conversion for you though we would encourage all clients to provide correctly formatted graphics since colour conversions can produce unpredictable results.

In the next part I will be focusing on CMYK and looking at the little idiosyncrasies of the system when it leaves theory and enters the world of ink and printing. These are things you’ll need to be aware of to achieve the best results for your printed CDs, DVDs and packaging items.