The primary purpose of the Light Box characterization mode is to create a compensation file that represents a light box non-uniformity and which can be used to correct target measurements made thereafter on this light box. A characterization should be performed before doing measurements in the Emission-Reader Custom chart and PatchTool file measurement modes, unless you already know that your light box has a perfectly uniform luminance on its entire surface! You will notice in the screenshot above that the measurements on the edges of the light box area are dimmer than those in the center area. The mouse pointer (NOT the red square) is placed over the location which was selected as the White Point (WP) and we see the corresponding PROCESSED L*a*b* value of (100, 0, 0). The screenshot above shows the interface after: • defining the Light Box area; • completing the Light Box characterization measurements; • assigning the patch with the highest “Y” as the WP (patch display contextual menu); • saving the Light Box uniformity compensation data file (RAW data) (LightBox_160Vx200H- mm_20Rx10C_2.txt) . Note: In this case, we kept the Scan exposure of 35 ms for automatically determined from the WP measurement. Note: A detailed Light Box characterization procedure is available in the Help manual. A screenshot of the CGATS file options export dialog is shown below. The Light Box uniformity compensation file is based on RAW, i.e. NON-PROCESSED, spectral data. The PROCESSED data, i.e. compensated for the light box WP, can be used to VIEW the light box uniformity in a file which can be opened like any reflectance data file. A screenshot of the exported processed file reopened in PatchTool is shown further down.

The selected patch, with a black square, corresponds to the patch under the mouse pointer in the Emission- Reader tool screenshot. The patch data in the Info window is also the same as the one shown in the Emission-Reader tool window, i.e. L*a*b* = (100, 0, 0) for patch ID = 110.