Colour management is the calibration and profiling of each device that digitally produces colour in a file workflow so that produced results are consistent from file capture, design, view, and print or output. Without this results can be somewhat random.

Sometimes peoples whole focus when attempting to control colour workflow can be on "Profiles", they are just a very small part of the equation. Every device and media or ink needs it's own unique profile to be accurate.

What is a "Profile"?

Profiles are a part of the method for conversion between varying colour spaces.

For example, while viewing a CMYK file on a monitor (an RGB device), there is no direct link between RGB and CMYK colours. There needs to be a translation in the middle that allows this to happen (cielab) plus a description of how these colours should look. Different RGB devices will produce colour differently to each other, and be different to other RGB devices like scanners or digital cameras. Likewise, CMYK will produce colour differently on different devices and media. Each specific output requires a description of how to accurately produce the colour in a digital file.

There are always 2 profiles in any conversion (with the exception of files created in cielab). There is an "Input or Reference" profile that describes what the file should look like, and an "Output or Media" profile that explains how to achieve that result. In between these two profiles is cielab to allow this conversion to happen.

A profile is a table that communicates colour. An example of this is a CMYK media profile for a printer, this would offer information as follows: "CieLab-->CMYK". On it's own it does not give enough information to complete the action. If you were using a RGB file then there would also be an RGB profile in use, and the full conversion would show as follows:

RGB --> CieLab --> CMYK

This conversion might actually be as follows in colour values for each conversion:

R=255 / G=0 / B=0    -->    L=54 / A=81 / B=70    -->    C=0 / M=99 / Y=100 / K=0

You can try this yourself in Adobe Photoshop: Create a new blank page and use the "Color Picker" tool. Enter 255 in the RGB "R" area and leave G&B as 0. You can see the different values across the spaces all in one screen.

"Screen grab taken from Adobe Photoshop"

Results will vary depending on the profiles you have selected in your Photoshop "Color Settings" area as your working spaces (you can view this by pressing Ctrl-Shift-K from Photoshop).

"Screen grab taken from Adobe Photoshop"

This also demonstrates the importance in your choice of colour settings even just while working on files in your design packages.

Compare profile creation equipment and software at cielab colourshop

What else is controlled in a profile?

A printer media profile controls other things like ink limiting, gray balance, linearity of colour and more:

Because the profile was specifically produced for the exact printer/ink/media combination you have loaded, it will use the precise amount required to produce colour (saving on ink consumption) but will also eliminate bleeding, cockling, pooling, and flooding.

It also knows how to lay down the exact CMY mix to produce a neutral gray without the use of any black ink at all if you choose. Many people have experienced printed gray results that have a coloured cast throughout. Some printer manufacturers add additional light black or gray inks to their printers to overcome this, although this is completely unnecessary in a calibrated and profile state and often adds to the running costs of the printer.

Another thing that is improved by using the correct profile is better linearity, or colour distribution. When using generic profiles, people often see "Posterisation". This is a visible line that appears between graduations of colour.

What are Rendering Intents?

The story doesn't end there, some profiles have a larger colour gamut than other profiles, so what happens to colour that can not be produced? This is where something called a "Rendering Intent" comes into action. It the way that colour is mapped between profiles. You may note that in my example above that i have selected "Relative Colorimetric" intent under conversion options. There are 4 primary rendering intents as follows:

Relative Colorimetric

• Will keep all producible colour as accurate as possible and forget any "out-of-gamut" colour (colour that can not be produced). This is the most commonly used intent for accurate reproduction of spot colours and also contract proofing in the offset printing industry. This is the best across-the-board setting to use for the print industry.

Absolute Colorimetric

• The same as Relative colorimetric although will map in a white point simulation. This is almost exclusively used in contract proofing for the offset industry where the proofing paper used on a digital proofer (carefully calibrated and profiled inkjet printer set up to exactly match the offset press) is usually much whiter than the offset stock used. This will print a light colour in the background of the file to closer represent the offset result.

Perceptual

• This rendering intent will maintain the majority of the colour that can be accurately produced but will move "out-of-gamut" colour into the edge of what can be produced. This means that the outside of the reproducible colour will change but you will maintain some shadow detail that would otherwise be lost. This setting is best used when working with photographs.

Saturation

• This intent follows the theory that as long as everything is bright and clearly the chosen colour, the rest will be likely to shift. This is best ONLY used in things like office presentations where spot colours and photos do not need to be produced accurately. This intent is used by windows (printer drivers etc).

If you convert a file from RGB to CMYK and use different intents the colour information inside the file WILL be changed and the output result will vary, this is why when consulting at a location with more than 1 computer that files travel through, that the manager make some well thought out selections for these setting and implement them as company file workflow policy. Even take a screen grab as I have done above and keep it in a manual for future reference. This will standardise what is being done and eliminate wasted labour and consumables trying to duplicate an earlier result with random settings.