I'll start out with some basic info about TV in general. The TV mixes three primary colors of light, red, green and blue to achieve the full NTSC spectrum of color. It accomplishs this using light output, (luninence) in combination with the phasing, (mixing) of the three primary colors, to obtain all of the different colors of the spectrum. The light output of a TV can be measured and organized into a standard called IRE. IRE is defined as:
IRE (Institute of Radio Engineers) 1 Volt Peak - Peak Video is divided up into 140 IRE units. This is done to make numbers for luminance levels easier to communicate. The amplitude of the video signal from blanking (zero volts) to peak white is 0.714286 volts or 100 IRE units. Synchronization signals extend from blanking to -0.285714 volts or -40 IRE units.
Picture Black Level: 7.5 IRE (above zero volts)
Picture White Level: 100.0 IRE (above zero volts)
Blanking Level : 0.0 IRE (zero volt level)
Burst Pedestal : 0.0 IRE (zero volt level)
Synchronization : -40.0 IRE (below zero volts)
Black was raised above 0 IRE in the early days of color television to get around some transmitter problems. The practice has been with us ever since.
The SMPTE component video system does use the IRE system to define video levels. It is based on a 700 mVolt system rather than the 714 mVolt composite video.
Luminance is defined:
Luminance This is the signal that represents brightness in a video picture. Luminance is any value between black and white. In mathematical equations, luminance is abbreviated as Y.
The characteristics of color information, independent of luminance intensity. Hue and saturation are qualities of chroma. Black, gray, and white objects do not have chroma characteristics.
The frequency that carries the color information in the baseband composite video signal. In NTSC the color subcarrier is 3,579,545 Hz, ± 10 Hertz. This number is usually rounded off in text to 3.58 MHz.
Unlike the black and white television standard, where the vertical and horizontal frequencies are derived from the 60 Hz power line frequency, the color subcarrier became the clock reference for the color system. The horizontal and vertical frequencies are now derived from the color subcarrier rather than the power line rate. When we shifted to the color system in 1954 the horizontal and vertical rates changed. The amount of change was small enough so that black and white sets would still synchronize to the updated rate.
A color sync burst of 3.58 MHz is added to the beginning of the horizontal lines to synchronize the color decoding circuits in the display device with the source video.
The phase of the color information in the video is changed 180° for every adjacent line. The change occurs automatically as part of the horizontal timing being derived from the color subcarrier. It has the overall effect of canceling the display of the color subcarrier in the picture. It does, however, produce "dot crawl" at color transitions.
It takes two complete pictures for the phase relationship between the subcarrier and horizontal signal to return to zero. (This presents a minor problem for laserdisc players when displaying a still frame. The color phase has to be electronically reversed every other time a single frame is repeated because a still frame is only half of a color cycle.)
Getting proper grayscale is calibrating gray to a reference standard (color temperature setting), across the IRE spectrum for the TV. The standard reference for movie studios is D6500K, where K is Kelvin, (the color of a flame at 6500 Kelvin). The shade of gray, (as measured against varing light outputs) will change as the IRE changes, producing an array of shades of gray and must be measured with a color analyzer to obtain accurate results, although you can eyeball the color of gray and adjust it "old school" style. You generally adjust cuts for low light output such as 20 IRE and 30 IRE windows, available on Home Theater tune-up DVDs such as AVIA. Drive adjustments are used for higher light outputs such as aan 80 and 90 IRE test windows.
Sorry for the long and winding road, hope it helps some.