I-Q

Refers to one method of encoding of the color content of a video signal such that all colors could be depicted using a two dimensional diagram, more specifically a color wheel. There are two color signals one (I) of which represents oranges and blues and the other (Q) represents greens and purples. (Both together are used to represent other colors.) This choice of colors permits giving the oranges and blues, which the human eye is more sensitive to, more frequency bandwidth and thus greater color resolution in NTSC video. The remaining colors had to be limited to about 48 lines of resolution (0.6 MHz sideband width) to keep there from being too much color information contaminating the medium detailed luminance information in the composite video signal. Many TV sets today and all consumer VCR's limit color resolution to a theoretical maximum of 40 lines for all colors. When it is not necessary to construct a composite video signal, the color signals U and V representing blue and red respectively, are usually used instead of I and Q. We believe that all of the descriptions on this page can be understood quite well by persons without tremendously high intelligence quotients. Click here for more on video signal formats.