What is a Reference Profile?
18/12/2003
While the ICC standard covers the entire process chain from image creation to image output and therefore recognises a number of different profile types, the output colour profiles are of crucial importance for working with Best Colorproof. For example, output profiles describe the colouring behaviour of LED printers, printing presses and similar devices.
The heart of output profiles for CMYK devices is a "look-up table" (LUT). This is a table listing a variety of colour values that could be used to activate the device. Each of these device-specific colour values (for example, in CMYK format) is compared with the CIELAB values that are measured when the CMYK value is printed. The CIELAB colour system is a device-independent, mathematically derived colour space that allows colours to be uniquely defined.
Best Colorproof, for example, uses two ICC output profiles for proofing:
· the reference profile, which describes the colour reproduction
of the printing press to be simulated, and
· the paper profile, which describes the colour reproduction of the
printer in combination with the paper and toners used.
In principle, these profiles are then activated sequentially so that the CMYK values for both output devices can be related to each other via a CMYK - CIELAB - CMYK link. The following diagram demonstrates this link:
This simplified version of the principle is, by itself,
insufficient to produce colour printouts of convincing quality, and
the profiles themselves already contain a great deal of additional
information describing the output device. Best Colorproof also
evaluates this information and, in addition, offers high-quality
screening processes for print output, base linearisation and
printer linearization, paper white simulations, render intents, and
much more.
