Show your true colours

David Braue
25 July, 2012
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It’s not every day that you’ll need to adjust the colour on your computer screen, but the good news is that when that time comes, Mac OS X offers a suite of colour-management tools to give you minute control over the way your Mac displays colour.

This control is helpful if you want to change the colour temperature of the screen’s display to match unusual ambient lighting conditions, or to expand the dynamic range of the images it produces. If you’re involved in content production, colour matching is also critical in ensuring that onscreen images match the inks used by your printer; every system of colour production works slightly differently and produces slightly different hues.

Just like Windows offers profile- based color management and screen calibration through the Control Panel > Color Management option, Mac OS X’s controls are accessible through System Preferences > Displays > Color.

You’ll initially see a list of colour profiles on your system. On our system, the default options included Adobe RGB (1998) – an ICC-based colour profile introduced with Photoshop 5.0 in 1998 – as well as Generic RGB Profile and sRGB IEC61966-2.1 (a global standard for multimedia systems published by the International Electrotechnical Commission). The final profile, Color LCD, is the default for your Mac and is calibrated for its LCD screens.

Use the built-in Apple Display Calibrator Assistant to automatically adjust your colour space: make sure your screen is at maximum brightness (press F2 until the brightness indicator reaches the maximum setting) then click Calibrate to start the calibration wizard.

The wizard walks you through several stages including native and target gamma adjustment (relating to the overall brightness of the screen) and white point adjustment (relating to colour temperature).

If you turn on Expert mode on the first screen, you’ll be guided through five extra steps to determine your display’s ‘native response’. You’ll adjust the target gamma – the system-wide default of 2.2 is usually adequate but you can change it if necessary – and target white point, with the colour gamut shown on the graph (a standard white point like D65, at 6500K, will often be fine but you can tweak it for unusual lighting situations or different external displays).

If you want to manually adjust the profile, select it from the menu and click Open Profile; you can page through the parameters of each profile and view the colour spaces, phosphor values, response curves and other characteristics of each profile. If you’re running more than one monitor, be sure to calibrate each of your displays to ensure that you’re running consistent colour profiles across each of them.

The calibration wizard is only one way of adjusting your system’s colour; profiles can be viewed and managed individually or, if you require, can be exchanged between computers – to ensure, for example, that all members of a team are seeing the same colours in a collaborative project. Colour files – with the .ICC extension – are stored in /System/Library/ColorSync/Profiles.

Run the ColorSync Utility (in your Applications/Utilities folder) to see all profiles installed on your system, and you’ll get a plot of the colour gamut for each one. You can also click on the Devices tab to check out the colour profiles installed for device such as cameras, scanners, displays and printers. Click Filters to check out the installed image-processing filters, or Calculator to map colour values between profiles.

If you’re doing a lot of work with colour, it’s worth pointing out the DigitalColor Meter application (in Applications > Utilities), which will tell you the RGB values of any onscreen element you can point your mouse to. You can use it for quick web colour- matching or to ensure correct colours when doing detailed image editing.

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