Working with visual digital media such as photography, video and graphics requires consistent and ideally, portable, colour models. Otherwise, what you see won’t match what you get when it’s printed out or viewed on the screen.
Smoothing out the colour differences is made difficult by the fact that disparate devices use varying methods of reproducing colours. For instance, monitors use the Red Green Blue (RGB) method, corresponding to the coloured phosphor triplets in CRT (cathode ray tube) screens. Printers use a different method to describe colour space, however: Cyan Magenta Yellow (CMY, sometimes CMYK with the last letter derived from the added Black).
Conversion between the different colour space models can be tricky, especially since the RGB one cannot display some visible colours (such as pure yellow) that CMY can, and vice versa.
Video uses its own colour space models, such as YUV, which uses combined RGB values to create a signal for the brightness of any given area, and then creates two colour signals by subtracting the blue (U) and red (V) from that. There are many more colour space models, including Hue Saturation Brightness (HSB) and the different CIE (Commission Internationale de l’Éclairage) standards.
Converting between models has been known to give the strongest people nervous breakdowns, so a standard method to describe colour spaces for conversion between different devices was needed.
Windows XP Professional uses International Colour Consortium (ICC, www.color.org) device profiles. These are binary files located in %windir%\system32\spool\drivers\color and carry information about the colour space for devices such as monitors, cameras, scanners and printers. ICC device profiles are an international standard, and can be embedded into files to provide information about how the device that created the image reproduces colour. Microsoft has licensed colour management module from prepress specialists Linotype-Hell called LinoColorCMM as the transformation engine for use with ICC files.
However, not all applications are ICC-savvy, and embedding the profiles is usually not done automatically, so it’s worth checking each time. Check the profile
Usually, an ICC profile is provided by the manufacturer of the device. To check if your monitor is using the manufacturer’s ICC device profile, right-click on the desktop, select Properties, and click on the Settings tab and the Advanced button there.
Under the Color Management tab, you can see which colour profile is used for the monitor (see FIGURE 1). If one is lacking, or it’s the wrong one, use the Add and Remove buttons to ensure the right profile is active.
Likewise, have a look in the Properties for your colour printer: there should be a Color Management tab there as well, pointing to an ICC device profile suitable for your printer.
You can usually find device profile files for downloading at the Web site of the manufacturer of your device. Adobe also provides device profile ICM files as a free download, to be used with its software. Check that the files in question are for the colour temperature you use (e.g., 6500° Kelvin) and, of course, that they’re for Windows.
Note, however, that manufacturer ICC profiles are what’s termed ‘generic’, which in simple terms means it’s an approximate fit for the model of device you have, and not calibrated specifically for your particular device.
In other words, if you’re serious about graphics and video, you need to calibrate each device in the processing chain — the scanner and digital camera, the monitor and the printer. This is something that has to be done on a regular basis, to compensate for equipment wear and tear as well as changes in the output media, such as different paper, film as well as inks and toner.
You can calibrate manually, using software and your eyes, but that’s a hit-and-miss method. Instead, it makes sense to use a colorimeter or spectrophotometer to accurately measure the RGB values, and software to automatically calibrate the screen and create an ICC device profile for it.
Colour printers are calibrated in a similar way — a print-out is read by a spectrophotometer to measure the colour values, with the results fed into a device profile. You can also use a high-quality scanner and a test image, and compare the print-out to that. It’s cheaper, but less accurate.
Digital cameras are a bit more complex to calibrate, as you have to take a picture of the test image with known colour values, as well as adjust the ambient light to the right temperature, and ensure the white balance of the camera is set correctly.