Color management with ICC profiles in practice.

One of the most frustrating moments in a graphics designer's life is when the beautiful blue on screen comes out of the printing press as something completely different. The reason is almost always lack of colour control. Each device — screen scanner printer printing press — reproduces colours its own way. Colour control is the system that binds them together so a colour means the same thing all the way through.

§Why colours shift

A colour defined as specific numerical values in a file has no fixed appearance in itself — it must be interpreted by a device. Two screens with the same numerical values display different colours because their screen panels are different. The same problem arises between screen and print. Without a common reference system colour is fundamentally a guess about what the numbers 'mean'.

§ICC profiles and colour spaces

An ICC profile (defined by International Color Consortium) is a data file that describes how a particular device or colour space renders colour. The profile translates between the device's own colour values and a neutral device-independent reference room (a profile connection room based on how human vision perceives colour). When both source and target have a correct profile a colour can be translated reliably from one device to another.

• 01A document/working colour space defines how the file's colour values should be interpreted.
• 02A screen profile describes how your screen reproduces color.
• 03An output profile (printer or printing press) describes the target's rendering.
• 04Color management translates between them via the neutral connection room.

§Calibration – the foundation

Color management is only as good as your screen. An uncalibrated screen lies about colors, and then no profile helps. Therefore you calibrate the screen — preferably with a measuring instrument — so it shows color predictably and you work in uniform, neutral light. Editing critical colors on a random, bright screen in mixed room light is building on sand.

§Rendering intents

Some colours in a large colour space cannot be reproduced in a smaller one – for example very saturated RGB colours that lie outside what print can handle. A rendering intent determines how colours outside the range are handled during conversion: some prioritize preserving the overall impression and soft transitions (good for photos), others prioritize precise, strong colour areas (good for logos and graphics). Choose intent based on what the image will be used for.

§Softproofing and agreed printing profile

Softproofing is when you simulate on a calibrated screen how the file will look in a specific printing process by viewing it through the print shop's output profile. This gives a realistic preview before anything is printed. Therefore it is crucial to agree with the print shop which color profile and which print standard applies — so you work towards exactly the rendering the press delivers, instead of guessing.

§Black, registration, and colour separation pitfalls

Color management doesn't solve everything — there are printing technical choices the profile doesn't control. For example how black is composed (pure black versus a deeper blend of several colors) and how much color total may be laid on top of each other before the paper can't dry. Discuss such printing technical limits with the printer and hold your choices up against their specification rather than guessing a number.

“Color management doesn't make colors perfect — it makes them predictable. And predictability is what separates a professional from someone who crosses their fingers at print.”

— Principle in applied color management