What is an ICC profile, and when do I need one?

An ICC profile is a description of how a particular device or colour space represents colour. It helps colour-managed software translate colour between a camera, monitor, design file, printer and material with predictable results.

Think of it as a translation reference. The same RGB numbers can describe different visible colours depending on the RGB colour space. The same CMYK values can print differently under different printing conditions. A profile tells the software what those numbers mean.

Where profiles are used

• Image profiles, such as sRGB or Adobe RGB, identify the colour space in which image values were created.

• Monitor profiles describe the behaviour of a particular calibrated display.

• Output profiles describe a printing condition, often a specific printer, ink set, media and RIP configuration.

What does a profile actually do?

A colour management system uses the source profile to interpret the original colour and the destination profile to work out how to reproduce it. When a colour is outside the destination gamut, a rendering intent helps determine how it is mapped into printable colours. A profile does not create colours that the printer or material cannot reproduce.

When do I need one?

Almost every serious colour workflow benefits from correctly identified source profiles. You should usually embed an appropriate source profile when supplying photographs or PDFs. However, you should not automatically assign a generic printer profile to your artwork. Your print provider may want to control the final conversion in its own RIP using a media-specific output profile.

Assigning versus converting

These operations are different. Assigning a profile changes how existing colour values are interpreted without changing the numbers. Converting to a profile changes the numbers to preserve the intended appearance as closely as the destination space allows. Incorrectly assigning a profile can cause a dramatic colour shift.

Common mistakes

1. Sending an untagged image and assuming the printer will know the intended colour space.

2. Treating a downloaded ICC profile as a magic fix for an uncalibrated monitor or unstable printer.

3. Converting artwork multiple times between incompatible spaces. Each conversion can change the available colours.

4. Using a profile for a different media, ink set or printer condition.

What should I send to my print provider?

Keep a copy of the original file, embed its correct source profile and ask whether the printer wants RGB or CMYK data. For colour-critical work, agree a physical proof on the intended substrate.

Bottom line

ICC profiles help make colour decisions repeatable. They are one part of a wider process that also depends on calibration, media, ink, lighting and production control.

Hudson Display Services can provide independent advice on wide-format profiling, colour workflow problems and artwork preparation.