What’s the big deal with CMYK? Can’t you just open an image in Photoshop, select Mode and convert to CMYK? It’s that easy, isn’t it? I wish it were but the truth is creating a high quality CMYK separation requires a particular skill-set and how you decide to convert your image from RGB to CMYK can make or break the quality of the printing job. With so much misunderstanding about this topic it is difficult to determine what is the correct path to take and on top of that printers do not have the resources to teach you how to create a decent CMYK file. But times are changing and so should the thinking of those putting ink on paper.

The best plan for the future is to be one step ahead of your competition and colour management will continue to be a reality for printers. Currently, standards are being developed to assist printers achieve more consistency on sheetfed presses. GRACoL7 is an implementation of the ISO 12647-2 printing standard, with metrics, methods and characterization data developed during seventeen research press runs at nine US printing sites over eighteen months. The goal of this initiative is to ensure greater consistency and predictability from one press run to another and once we have locked down a standard we can distribute an ICC profile describing the process. Consider the implications of standardized printing: easier and more consistent CMYK conversions, realistic soft-proofing and more accurate desktop proofs. No more closed loop colour.

But until take day arrives we have to deal with what is available today.

Below is a short list of the tips and thoughts on the subject of creating the best CMYK file:

More responsibility is now in the hands of the content creators. Good or bad

CMYK is device dependent. Meaning there are many flavours of CMYK. One size does not fit all.

Repurposing a file from RGB to various CMYK colour spaces makes sense. Keep your master file in the largest colour space possible, RGB.

Not honoring an embedded profile (Adobe RGB and using your default working space sRGB) can cause significant degradation to a conversion!

If you are working with a printer on a regular bases start a dialog, ask about acquiring a press profile or a profile of their proofer.

Lightness and darkness are the one of the biggest variables on press and is called Dot Gain or recently Tone Value Increase TVI. There are many variables about printing you cannot change and must be accepted. Variations will occur. The printing process is not an exact science.

Paper should be considered the fifth colour in CMYK printing. Paper white/colour has a Huge impact on the outcome. Be aware of the power of the fifth colour.

Asking your printer how to create a good CMYK separation is like asking your IT staff for the servers’ password. Mums the word.

Supplying a proof from your RGB file printed on a desktop inkjet is asking for trouble unless it has been properly calibrated and profiled or runs through a software RIP. Printing default RGB produces darker, richer blacks, more vibrant colours, not achievable on press.

Don’t supply proofs on inkjet media that is glossier and whiter than the press sheet. Give the client the bad news early by showing them a realistic proof. Set sensible expectations.

Basic Target colours:

Catch light, reflection or spectral highlights: an area with no detail C=0, M=0, Y=0, K=0

Highlight: Lightest area with detail should be C=4 Y=2 M=2

Midtone Gray: A neutral 50% gray should read C=50 M=42 Y=42 K=6

Shadow: Darkest area with detail. (Dependent on your total ink limit) For SWOP the numbers are C=75 M=68 Y=67 K=90. 90-95% is the maximum amount. Anything more will likely fill in – no detail.

CMYK is a small colour space and enhancing particular colours is required to ensure your images have the necessary punch or shelve appeal but going too far and you loose detail and shape. Learn what colours contaminate certain colours – colours opposite on the colour wheel are contaminates and removing that colour will increase the saturation.

Cyan: Skies are made up of a lot of Cyan and a little Magenta. Keep Yellow low in these colours. Yellow will just dull the blue sky.

Reds: Needs a bit of or Black for detail. Y=100 and M=100 makes a Yellowy red M=100 & Y=90 is a better red.

Blue: Too much Magenta will push the colour to purple. Keep the Magenta component under 80% for a rich blue.

Green: Grass and leaves require at least 10% Magenta - remove too much magenta and your grass will have a day-glow look.

Skin tones: You need a third cyan and equal amounts of magenta and yellow. Yellow can go a few points above magenta but the opposite (higher amounts of Magenta) yields a sunburned look.