The Canon imagePRESS C1+ is a digital press capable of printing four-color process toner, as well as a special clear toner. This clear toner can be used to create watermarks in images for security printing as well as elegant designs. When printing this clear toner over or under other colors, it is imperative to understand how it will affect their color gamut, because it can change how an image looks. This change can even be observed with the human eye.
To determine exactly how clear toner affects the color gamut, the imagePRESS first needed to be profiled correctly in order to achieve accurate results. The chart used for this was the ECI2002R CMYK test chart. Before profiling, a set of five substrates was also chosen. Substrates used include one with a smooth finish, one with a gloss finish, and one with a matte finish. These substrates also varied in weights, giving an extensive range of options to compare. Each substrate had three different samples; one printed with no clear toner at all, one with clear toner underneath the CMYK toner, and one with clear toner on top of the CMYK toner. Thus, fifteen different profiles had to be created.
Once these profiles were created, their color gamuts could be viewed and compared using software. The GretagMacbeth ColorChecker(r) was also printed, with each profile applied, on the corresponding substrate. From the GretagMacbeth ColorChecker(r), color measurements were then taken and compared. The measurements taken include the LAB values of each color square in order to determine the DE between using and not using the clear toner.