Comparison of xvYCC Color Space with Traditional Specification
The Munsell Color Cascade provided by Michael R. Pointer is a highly saturated color chart consisting of 48 hues and 16 levels of lightness for a total of 768 colors. Figure 3.1 provides two-dimensional and three-dimensional representations of chromaticity points in the actual color chart and the color chart for the color space. Figure 3.2 uses this data to show the color representation capacity of the xvYCC standard. It is difficult to represent the xvYCC color space on a two-dimensional x,y chromaticity diagram, which is an x,y projection of the three-dimensional color space. We will therefore explain it in three-dimensional space, using x,y chromaticity and luminance (z axis). Chromaticity points (black dots) in this color chart form a triangular pyramid, with color points spreading out where luminance is low.
Figure 3.2 shows the relationship between the color space in the existing BT709 standard and color points in the color chart. Here, some color points in the color chart are excluded from the color space in the BT709 specification. The enclosed area is equivalent to 55% of the 768 colors in the color chart. The gray area in the color chart denotes colors that cannot be represented under the BT709 standard.
Figure 3.3 provides a three-dimensional image of the color space of the xvYCC standard. There are four peaks representing areas of high luminance, while the width of the graph expands as luminance decreases. This means that the entire color chart can be encompassed, and that 100% of the color chart representing highly saturated object colors can be represented under the xvYCC standard.
Extended Color Gamut in Display Devices Based on xvYCC Specification
As described above, a CRT TV based on the BT709 standard can only represent 55% of the Munsell Color Cascade (see Figure 4.1). In 2006, Sony launched BRAVIA, the world's first LCD television based on the xvYCC standard. An LCD TV with LED backlighting can represent 82% of the Munsell Color Cascade, while a Sony GxL projector with a laser light source can represent up to 97% of the colors (*3) (see Figure 4.2 and 4.3). This is indicative of the performance that can be achieved when the xvYCC standard is applied to extended-gamut display devices.
*3 As of November 2005, based on Sony research.
The Future of the Technology
In 2007, Sony also launched the world's first digital video camera capable of recording xvYCC color signals. This allows images of objects with highly saturated colors, such as flowers, cars and stained glass, to be captured more realistically then ever before.
Sony has announced the designation "x.v.Color" for products that can process color signals based on the xvYCC standard to represent a wider color range or "gamut" than is possible under the existing standard (BT709). This logo is applied to products that have this capability. Other manufacturers have also started to use this logo, indicating that the use of the xvYCC standard in consumer electronic products is increasing. The DCDM digital cinema standard has already been formulated for video content with a wider color gamut than BT709, and content is now being produced. The shift to extended-gamut display devices and the increasing use of the xvYCC standard are likely to drive the shift toward extended-gamut content. It is hoped that the xvYCC standard will also be applied to technology for the equipment needed to produce and distribute movies, broadcast content, packaged media, and network content.
