Specifying icHeader.manufacturer and icHeader.model tags is all that is needed to install a single ICC profile for a given device. However, because a device may produce measurably varied results for the same color profile when configured differently, it may be useful to map multiple profiles for different configurations of the device. The optional profile tags described later in this section make this mapping possible when the printer configuration changes at run time.
The number of possible profiles directly maps to the matrix of possible configurations of the device. The issue of how profiles are chosen if an incomplete matrix of profiles is installed is discussed in a later section. For example, a printer model with 2 possible media types, 2 possible dither/halftone types, and 2 possible resolutions could have as many as 8 different profiles (2x2x2). Because profiles may not exist for each combination of configuration possibilities, there can be "an incomplete matrix of profiles."
Using optional tags enables Windows to differentiate printer configurations based on these variables, and the values these tags assume are closely tied to how the device driver reports these configuration differences to Windows itself. The optional tags correspond to the possible output media type used, the dither/halftone algorithm currently selected by the device driver, and the selected output resolution of the device. Information about each of the optional tags is listed below.