Measuring the color capability of modern display systems

Abstract

Historically displays used three colorants in an additive system. During that time, the CIE chromaticity diagram adequately illustrated color capability. Modern displays are not constrained by this additive architecture, and the diagram can fail in its purpose. This is demonstrated by analysis and a large number of display measurements. A device‐independent methodology using CIE 1976 L*a*b* color gamut volume is described that provides a robust means to determine the size of the color gamut. This methodology is then extended to the ‘gamut rings’ diagram as a solution for visualizing color capability that directly correlates to color gamut volume. It is further shown how the methodology can be applied to determine the intersection between two gamut volume boundaries.

Gamut rings of reflective ePaper displays with combined frontlight and ambient illumination

“…For example, if the display is known to reproduce only five image levels, then it will be sufficient to subdivide the input colour into a 5 × 5 grid. The CIELAB color gamut envelope is derived from the measured colors that were uniformly sampled from the surface of the RGB signal cube, and the volume determined through tessellation 10,14,18 …”

“…Recent research on emissive displays demonstrated that a display that can produce colors over a wider range of luminance may yield a larger color gamut volume, but not necessarily a larger chromaticity area. 13,14 However, it is important not to interpret this as color quality perceived by a human observer. The gamut volume is only one measure of color capability, the capability of a display to produce a range of colors in CIELAB.…”

“…The CIELAB color gamut envelope is derived from the measured colors that were uniformly sampled from the surface of the RGB signal cube, and the volume determined through tessellation. 10,14,18 Once the gamut volume envelope is determined, the CIELAB color gamut volume can be represented as a 2D gamut ring diagram as shown in Figure 5. 13 The gamut ring diagram is derived from a display's measured CIELAB envelope by first dividing the volume into ten equal slices along the L* axis.…”

“…Recent standards have proposed representing the CIELAB color gamut envelope in two dimensions, in a so-called Gamut Ring diagram. 10,[13][14][15][16] The CIELAB color gamut volume method with its 2D Gamut Rings representation was originally demonstrated for self-luminant displays. However, reflective displays require a different implementation of the gamut volume method.…”

Overview of the Newly Released IDMS

“…As reinforced in recent publications, 3,4 and as explained in the new IDMS (section 21.3.2), color gamut is a volume ∗. It is critical to use three‐dimensional tools that consider the lightness axis, in addition to chromaticity, to properly represent any display's color capability.…”