Building a device profile is conceptually quite simple. In the case of output devices (in this context, the monitor is an output device), the profiling process consists of sending known RGB or CMYK values to the device, then measuring the CIE-based device-independent color they produce with a spectrophotometer or colorimeter. In the case of an input device such as a scanner or digital camera, the profiling process involves scanning or photographing a target that contains known CIE-based values, such as a reflective or transmissive IT8/7.2. The profiling software then compares the device-specific values with the device-independent color they produce, and builds a device profile.

Scanner profiling

To create a scanner profile, the first step is to scan the IT8/7.2 target. This target has two components, the physical target itself on transparency film or photographic paper, and an accompanying reference file that contains CIE values measured from the target. The scanner profiling software then compares the RGB values the scanner recorded with the CIE values in the reference file, and builds a scanner profile. Note that the profile is valid only for the scanner settings used to scan the target. You may wish to create several profiles for the same scanner to deal with low-key, normal, and high-key images, for example.

Monitor profiling

Monitor profiling software displays a target on screen that indicates where to attach the measuring instrument, usually a colorimeter or spectrophotometer. It then displays a series of known RGB values, and records the CIE values that the monitor produces from these RGB values. Some monitor profiling tools simply characterize the monitor (they measure it, but don't change its behavior in any way) while others allow you to both characterize and calibrate the monitor (they allow you to choose a target gamma and white point, then change the lookup tables in the video card to make the monitor produce that white point and gamma).

Printer and press profiling

In concept, profiling a printer or press is similar to profiling a monitor. You print a target containing known device-specific values (usually CMYK or CMY, though film recorders are RGB devices and some inkjet printers act as RGB devices), then measure the CIE values from the printed results with a spectrophotometer or colorimeter. In practice, however, building an output profile is considerably more complex than profiling a scanner or monitor, simply because the printing process involves a great many more variables.

In addition, since printing devices generally have a relatively small range of printable colors (often referred to as the color gamut), printer profiles contain instructions for handling out-of-gamut colors. The ICC profile specification contains four different rendering intents which offer different methods of handling out-of-gamut colors, but the rendering intent most often used for images, usually referred to as perceptual rendering, is subject to decisions made by the user at the time the profile is built. With CMYK printers, black generation, the proportion of black ink to the cyan, magenta, and yellow inks, also has to be specified by the user, adding yet another variable. Hence printers and presses are significantly more challenging to profile than are monitors or input devices.