How to Measure Color Gamut Volume with a Colorimeter?

Color gamut indicates the ability to display colors for a display system. Measurement of the color gamut in three-dimensional color space is important for a display system. Compared with the primary triangle in CIE XY or CIEu’v’ chromaticity diagram, the influence of brightness is considered, and the three-dimensional color space is more uniform, which is closer to the actual situation of the display system. In this paper, using a colorimeter, we propose a new method to measure the gamut of three primary display systems by measuring some feature points. They are located on vertexes, edge sand surfaces of the three-dimensional gamut boundary. Based on these feature points, the profile of the gamut is drawn in CIExyY and CIELAB space.

To calculate the color gamut of the display system, the traditional method is to calculate the area of the primary triangle in CIExy or CIEu’v’ chromaticity diagram CIE recommended the Segment Maxima algorithm to calculate the color gamut. The specific process is to sample three primaries through many images, then select outermost points of the color gamut and connect them into boundaries in CIELAB color space. It has been reported that the gamut volume could be measured by a colorimeter. Compared with the algorithm, our measurement method is relatively efficient. The accurate gamut of color solid is obtained in CIELAB space.

In general display equipment, the intensity of each primary is divided into 256 gradients (which are not nonlinear corresponding to the lightness value).

The measurement is performed in a dark room. The required colors are generated by software Microsoft paint and MATLAB. CS-2000 colorimeter of Kanica Minolta is used to measure the coordinates with the perspective of0.2°. The coordinates of each color are measured many times and the average value is taken.

We measure the color gamut of three primary laser display systems and LCD computer screen in CIELAB space as an example. We compare the results with gamut volume by theoretical calculation in CIELAB space.

Comparison of theoretical value and measured value (color line)of color solid. Above is laser display, below is LCD display as shown in the picture, the measured value is consistent with the theoretical value.

The result is, we present a method to measure gamut volume of a display system by measuring 19 feature points of color solid with a caliber 4mm handheld color meter: Compared with the traditional method, our method is more efficient and can be easily extended to four primary display systems. Further research on this algorithm can help us to map the gamut between different display systems.

Handheld Color Meter

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