Guest Column: Believe Your Eyes: Superior Color for Home Video
Audio experts understand that the quality of sound is strongly influenced by the physical aspects of the listening environment. They have developed tools to optimize sound quality and preferred surround effects, i.e., concert surround or rock band surround, for specific room characteristics.
Video quality is quite similar. Room lighting, screen size, screen brightness and viewing geometries all have a significant impact on video quality. All motion picture studios understand this aspect of video quality. They spend a significant amount of time and money tuning the quality for darkly lit movie theaters. Homes are not lit like dark theaters, and although consumer media releases do include some compensation for the differences in lighting, they cannot accommodate fully for visual adaptation, light variations from room-to-room, different room light color or room light glare. These all can cause dramatic losses in video quality. Video experts know this, as do consumers who see higher video quality in movie theaters than their homes, but standards and tools have not been available to provide solutions.
That’s all changing. Superior color for home video that accounts for the losses in visual quality in variable room lighting has arrived. 3D, multi-dimensional color processing technology, is now available with full modeling room lighting, viewing environment and visual adaptation. This technology can now take advantage of the increased color capability of displays and projectors to take the home entertainment experience to a whole new level.
Why Is Visual Adaptation Important?
The adaptive characteristics of the human eye are a major element in the viewing experience. Vision is a relative sense in that the eye sees colors and objects relative to what is around them and relative to how it has adjusted to the overall light it is looking at. Everyone knows that the eye pupil opens when it is dark and closes when is bright, but the relative adaptivity of the eye is much more subtle. Colors look more saturated when surrounded by bright backgrounds (see Image 1). The colors are exactly the same in the white and black backgrounds but your eye automatically sees different colors. It is unconscious like all visual adaptation.
Images lose significant color and contrast when viewed in dark rooms and bright rooms. Image 2 shows another example. The center patch is the same brightness for all the surround steps but it does not look that way. The patch looks like it gets darker as the surround gets brighter and the contrast between the center and the surround increases perceptually.
You also can see things that are much brighter than the brightness your vision adapts to. For example, if your vision is adapted to the brightness of daylight, the glint off jewelry is much brighter, i.e., it sparkles. This is also why stained-glass windows appear to glow in a dark church once your vision adapts.
For motion picture theaters, this loss in color and contrast due to the visual adaptation to a dark surround caused film and digital system designers to introduce significant increases in overall system color and contrast to compensate.