TV Convergence


CRT projection televisions will have a convergence control. Convergence is the critical alignment of the primary video colors represented by the three CRTs that produce your picture. When convergence is misaligned you'll notice red, green, blue or combinations of all three out of place, and halos or ghosting can be noticeable. Your TV's convergence control will usually present you with white crosshairs placed in key positions on your screen; professional convergence patterns like the one pictured below are more complex.
The remote control or front panel will allow you to move one of the three colors at a time. You must move the colors around on the convergence pattern (crosshair) so it looks white without any colors bleeding off the edges. Typically, you'll control each color horizontally and vertically. You might even be able set the bow and skew - these are opposite directions that allow you to bend the images to get them aligned onto the test pattern.

Convergance screen
Typical professional convergance screen.

The biggest challenge with convergence is the game of sacrifice. You'll be forced to make trade-offs in order to get converge right on one area while sacrificing a bit of convergence of one color in another. Convergence is almost impossible to set perfectly even by professionals and it's very easy to get it hopelessly disjointed. Use caution when entering the convergence setting on your television; take a good look at the owners' manual so you understand how to use the controls.