The CIE Diagram shows the absolute color temperature and color points of the display’s primary red, green and blue colors on the graph’s X and Y axes. The area of the triangle represents the colors that should be reproduced by an HDTV, as specified by the Society of Motion Picture and Television Engineers (SMPTE). The primary colors specified by SMPTE are represented at each corner of this triangle. Various combinations of these colors would fall within the area of the triangle. Yellow, for example, would land halfway between the red corner (lower right) and the green corner (upper middle). Gray is in the middle. Ideally, the primary colors of a TV, represented by little colored dots, would land exactly at each corner of the triangle. A sub-triangle created by a TV’s primary color-point measurements would represent the colors that the TV is capable of reproducing. If the color points fall within the borders of the SMPTE triangle, the subsequent sub-triangle will also fall within those borders. The area of the SMPTE triangle that doesn’t overlap with the TV’s sub-triangle represents those colors that the TV is not capable of reproducing.
The graph should be 3-D, with the Z-axis representing intensity from white to black. (The Z-axis would contain the same data shown in the Color Temperature vs. IRE graph.) Excel’s limited graphing capabilities prevent us from creating a real 3-D chart. We show the color temperature measurement on the CIE diagram as a series of dots in the middle of the triangle. These are the same points measured in the Color Temperature vs. IRE chart, but they are turned on end to indicate toward which color the display leans. Ideally, all the measurements would overlap at a single point near the center of the triangle, which would be at the D6500 Kelvin point (X is 0.313, Y is 0.329). The color temperature may lean toward a different color at different intensities, which is difficult to notice both on the graph and on screen. However, if a majority of the dots drift toward one color, such as blue, the image will appear blue.