Got white? Now I mean the real white - not just any white will do! If your display doesn't have the real white, then you absolutely don't have the real colors! The NTSC (standard TV) and ATSC (digital TV) television systems are both based on a color system that uses a very particular color of white as its starting reference point. The accuracy of all the other colors produced in these systems depends on the color of white that is used as the "canvas," which affects the look of all other colors painted on it.
Think of a watercolor artist who has carefully chosen her colors to accurately represent her desired subject. The artist will get very wrong results, however, if she uses blue-tinted or red-tinted paper instead of a neutral white paper. It's just the same with video displays. If the color of white on your display isn't the same color of white the cinematographer (artist) used when he chose his colors, there is no way that your display can re-paint the artist's scene with the accuracy and beauty that the artist worked so hard to show you.
So what is the right color white? In 1931, the Commission Internationale de
l'Éclairage, or CIE (that's International Commission on Illumination for
most of us on this side of the pond), developed a method of precisely
specifying any color that humans can see. The method they developed was a
mathematical x-y graph plot (figure below) of all the visible spectral colors (the colors on
the curved outside border line) and of all the possible results of mixing these
colors (all the colors inside the border). Any one of these colors can be
specified by its x and y coordinates on the graph.
At x=0.333 and y=0.333, for example, is the equal energy white point (E). This color of white is what results from mixing equal energy amounts of all the colors in the visible spectrum. The CIE also defined a number of standard illuminant colors, which all fall in the center, near-white region of the diagram. Standard Illuminant A is the color of a clear 60 watt bulb. Several standard illuminant colors related to daylight were also defined; D50, D55, D65, and D75. These represent the color of daylight at different times of day and with different sky conditions, with D50 being more reddish and D75 being more bluish. The NTSC and ATSC chose D65 as the standard white color to be used with our television systems (D65 is equal to the color of light coming off a totally snow covered scene on an overcast day).
More important than which color of white they chose as the reference, is that all parts of the system use the same white reference. All displays need to be calibrated to have the same white background color (D65). Otherwise, all the other colors would get shifted from one part of
the system to the next. Luckily, all parts of our video distribution systems
are under very precise control. That is, except the very last piece, our
consumer video displays. Here, it seems, anything goes! Whatever it takes to
make the display more appealing on the showroom floor, no matter if we have
mucky blacks, blooming picture highlights, blue-colored grass, orange-looking yellow jerseys, and glaring red when we should see subtle shades of
color.