Picture Perfect: TV Calibration Demystified Page 2

Tools of the Trade A calibrator has several tools that are critical to properly adjusting your TV. He might use some test DVDs to create the necessary test patterns, but a high-definition video signal generator, which enables him to precisely calibrate different resolutions, is even better.

Picture Perfect: TV Calibration Demystified: The Equipment
A Sencore VideoPro multimedia video generator (left) creates the high-def test patterns, while a SpectraScan PR-650 colorimeter measures the screen's color temperature.
The most important tool is the one for measuring and adjusting the TV's color temperature. This can be an optical comparator (either a box with a fluorescent light bulb whose color temperature matches the NTSC standard or a small, properly calibrated monitor), a tri-stimulus color analyzer, a spectroradiometer, or a colorimeter. The optical comparator is the hardest to use and, because it relies on the calibrator's subjective judgment, gives the least accurate results.

The first thing the ISF technician will adjust is your TV's basic controls: contrast, brightness, color, tint, and sharpness. (For tips on doing this yourself, see Step by Step: How to Calibrate Your HDTV.) Typically this is done in your set's service menu, where the calibrated profile can be recalled if the user settings are changed. To get to these menus, you usually need a code from the manufacturer that you enter using the remote and the TV's front-panel controls. But be warned! Since service-menu adjustments can ruin your TV, only a pro should do them.

A Whiter Shade of Pale Like any color, white comes in more than one shade (see Grayscale Matters). In video, white is measured in kelvins (degrees Celsius above abolute zero), ranging from 2,800 K (the reddish-orange color of a 60-watt bulb) to 10,000 K (the purplish-blue you see in some headlights). The National Television Standards Committee (NTSC) that framed our system for analog color TV decided the correct shade of white is 6,500 kelvins - the color of sunlight at noon on a clear day - and the Advanced Television Standards Committee (ATSC) responsible for our digital TV system carried over the same color temperature as a reference point. More accurately, it specified point D65 along the "black body" curve of the CIE Chromaticity Diagram, and the correct color of white is expressed as points along the X and Y axis of the color spectrum (x = 0.3127, y = 0.3290).

Since a video signal is mostly black and white (or luminance), any deviation from D65 - whether toward the red or blue end of the spectrum - will bias the picture toward that color. The monitors used for color-correcting TV shows and DVD masters are also calibrated to D65, so your TV needs to be set to that color temperature if you want the images you see to match their sources. This setting isn't user-adjustable (except possibly by means of rather crude presets), so this is where the ISF calibrator really earns his keep.

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