Systems and standards
Colour management
The system of profiles and conversions that keeps a colour looking the same from camera to screen to printed page.
Presented by ClearTrust Free for designers, students and the curious.
Colour management is the set of methods that keeps colours consistent as an image moves between devices. A camera, a monitor and a printer each have their own way of turning numbers into colour. Each device is measured and described in a small file called a profile. Software uses the profiles to translate, so that the same red appears, as far as each device allows, at every step.
The problem
Send the same RGB numbers to two different screens and you get two different colours, because their red, green and blue lights differ. The same is true of printers and inks. Without correction, a photograph edited to look right on one screen will look wrong everywhere else. Before the 1990s each maker solved this in its own way within its own equipment. In 1993 a group of companies including Apple, Adobe, Kodak and Microsoft formed the International Color Consortium to agree on a shared format that worked across makers.
Profiles
An ICC profile describes how a device's numbers relate to real, measured colour, expressed in a device-independent space such as CIE Lab. To show a picture, the software reads the profile attached to the file, converts the values to real colours, then uses the screen's profile to work out which numbers to send. If a colour falls outside what the destination can produce, a setting called the rendering intent decides what happens. One option clips only the unreachable colours. Another squeezes the whole image gently so that the relationships between colours survive.
Doing it yourself
For most people this now happens automatically. Phones and current browsers are colour managed. Those who need accuracy calibrate their monitors with a small measuring device that sits on the screen and builds a profile. Screens drift with age, so the process is repeated every few weeks or months. Before sending work to print, designers view a soft proof, an on-screen simulation of the printed result using the printer's profile. Good habits help as much as equipment: steady, neutral room lighting, a grey desktop background and a profile kept attached to every file.
How to do it
- Leave the screen on for half an hour, then calibrate it with a hardware measuring device.
- Work in a room with steady, neutral lighting and no strong colours behind the screen.
- Keep a colour profile embedded in every image you save. Use sRGB for anything going on the web.
- For print, ask the printer for their profile and view a soft proof before sending the file.
- Check a printed proof in daylight or under a daylight lamp.
Sources and further reading
- Color management on Wikipedia
- International Color Consortium: About ICC
- International Color Consortium: Frequently asked questions
- W3C: A Standard Default Color Space for the Internet, sRGB
Original text by the Rang desk, written with AI assistance and checked against the sources above. Meanings of colour vary from place to place and person to person. If we have something wrong, tell us.