Updated 4/5/04
What is a tint control?
Actually there are two kinds of tint controls. One changes the overall look of black and white programs from bluish to brownish; we won't be discussing this kind here.
The other is also called a hue control or a color phase control. The name "color phase" comes about because the color signal in NTSC composite or S-video consists of a (n approx.) 3.58 Mhz signal whose phase specifies the exact color for each spot on the screen. (Depending on how fast the color changes, color information may be found anywhere in sidebands extending from about 2.1 Mhz to 5.3 Mhz.)
The color phase control is peculiar to composite and S-video. It is not applicable to RGB or what we refer to as component video (color difference video).
Think of a color wheel with, say, red at the top and yellow, green, cyan, blue, magenta, and back to red going around the circle. Black and dark colors are at the center and pastels are further out. As the electron beam paints the screen one scan line at a time, imagine a clock hand that can grow and shrink in length and which spins around the wheel (reversing direction allowed) to point out what color should be painted.
Adjusting the color phase control is like turning the color wheel slightly. For example when you make all the reds a bit purplish, all the greens become yellowish and all the blues become greenish at the same time. Assuming both the broadcast (or disk or tape) and the TV circuits are correct, once you get the flesh tones right, everything else should be right also.
Whether a signal waveform is in phase or out of phase is measured in degrees from 0 to 360 in the same way that position around a circle is measured in degrees. While the TV set has its own reference as to what is considered in phase, there may be differences from one broadcast station or VCR tape to another, as well as the viewer's personal preference. VCR head drum rotation and laser disk rotation is not perfectly uniform and a warped disk will play back video with added color phase errors also. This shows up as nonuniform color from one scan line to the next in a solid color patch and is referred to as chroma noise. The TV set with its fixed reference for "in-phase-ness" cannot correct this. The "time base correcting" and "noise reducing" chroma circuits in some laser disk players synthesize a floating in phase reference to better determine which phase changes are really color changes as opposed to disk rotational imperfections. DVD's contain numbers, not waveforms. Whether the numbers are read slightly faster or slower (within limits) due to nonuniform disk rotation does not affect the color, thus DVD playback does not have chroma noise problems of this kind.
TV sets also have individual controls for red, green, and blue which you can adjust with more or less difficulty.
Incidentally chroma horizontal resolution can be described as the limit to how fast the clock hand on the color wheel can spin. You can think, as the end of the hand goes from one color to another, all the colors en route get smeared on the screen as well. Color resolution capability is exceeded when the hand doesn't get all the way to the desired color when the time comes to start moving in another direction, towards another color. Luminance resolution is represented by how fast the hand 's length can grow (point towards pastels) or shrink (point nearer to black).
All parts (c) copyright 1999-2004, Allan W. Jayne, Jr. unless otherwise noted or other origin stated. All rights reserved
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