ICC output profiles refer to color gamut of printers and film recorders.

All printers use CMYK inks (or variations thereof), but with current operating systems, some of them (non Postscript ones) can only receive RGB data (which the driver internally converts to CMYK), and are therefore considered RGB printers.

An output profile:

• is two-directional, so can be used as either origin or destination;
• three rendering intents are required;
• may be RGB or CMYK, depending on the type of printer;
• must be in table form, from RGB or CMYK to lab.

The rendering intents of an output profile are implemented with different tables. All output profiles must have these six tags:

• from device to PCS:
  • AtoB0: perceptual;
  • AtoB1: relative colorimetric;
  • AtoB2: saturation;
• from PCS to device:
  • BtoA0: perceptual;
  • BtoA1: relative colorimetric;
  • BtoA2: saturation.

Thus, there may be up to three tables from device coordinates to PCS and up to another three in the opposite direction. In practice, more than one tag can (and almost always does) refer to the same table.

The PCS to device part is used when the profile is a destination profile (e.g. conversion from monitor RGB to printer CMYK). When the profile is used by the CMM the user has chosen one of the rendering intents (in most cases perceptual o colorimetric), so the CMM will only use the relevant BtoA table and, from the Lab coordinates of a color, will work out the corresponding CMYK values.

The device to PCS part of the profile comes into play when the device is used as the source device, e.g. hard or soft proof. For hard and soft proof, the colorimetric table is important: it is better that the AtoB1 tag refers to an actual table.

The AtoB0 and AtoB2 tables (device to PCS for perceptual and saturation) are only rarely useful. For example, when the destination profile does not contain tables for rendering intents, the origin profile must carry out the requested rendering.

In an output ICC profile, there may be two curves, before and after the table. The curve on the CMYK side may be used to limit the total quantity of ink: for example, everything over 95% can be rounded down to 95%, and everything under 3% rounded up to 3%.

On the Lab side one can regulate the saturation, color cast (a and b) and contrast, as well as brightness and clarity (L).