Modern ink-jet printers often provide more than 4 print heads. The additional channels can be used for faster printing, diluted process colours or additional dyes (green, orange). A proprietary gamut evaluation program is used to investigate the benefits of diluted inks vs. the addition of colours. The experiments are made using a four- ink printer. The eight-ink system has to be simulated by specially designed colour wedges that are printed with 4 inks each and are later assembled into colour space ribs. The colour gamut is calculated as the colour space volume sustained by the ribs using a spectral interpolation technique. The evaluation includes colour gamut size, tone reproduction and image quality criteria as well as permanence considerations.
Eduard Baumann, "Optimizing Ink Jet Dyes and Dye Dilutions for Color Gamut" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP16), 2000, pp 787 - 790, https://doi.org/10.2352/ISSN.2169-4451.2000.16.1.art00092_2