Only a black background was used behind the plates. For Pz-sap, the same variables were considered but the background color was changed (natural light background [NL], and white background [W]). Thus, the independent variables gave
rise to four different protocols for Pz-ph (DC/1C; DC/3C; CP/1C; CP/3C) and eight protocols for PZ-sap (DC/W/1C;
DC/W/3C; DC/NL/1C; DC/NL/3C; CP/W/1C; CP/W/3C; CP/NL/1C; CP/NL/3C).