Also called picture, contrast represents the total light output of the picture. Setting contrast too high will obscure fine details and if your TV is CRT or plasma it will shorten the lifespan.
Contrast is usually overdriven by factory defaults and purposely left too high in the store. Manufacturers reason that the TV with the highest light output will get the attention of shoppers. If you bring a new TV home you might notice contrast is set to 100%; this should be turned down to around 50%. At first, your eyes might miss that extra light from the picture but set the contrast properly against certain images and you'll see what you've been missing.
Contrast test pattern sometimes found on DVD extras.
In lieu of a test pattern, an image like the one below showing fine details between black and white will suffice. Pause a suitable image on a DVD, turn the color control all the way down so you only see grayscale (black and white). Now you're ready to begin setting contrast.
Delicate details in sand can be used to find perfect contrast.
Start setting contrast by turning the contrast down until the picture looks too dark. Bring contrast back up slowly.You'll notice there is a point where the fine lines between black and white become blurred - this is where contrast is too high. Once this is set correctly, more detail will emerge. Explosions, flame, ice, snow, wrinkles in a shirt all contain details that get glossed over when contrast is too high.
If your TV is older and you find that you cannot set the contrast high enough, this could be a sign that your TV has outlived the picture tube. If your TV's contrast control has an obvious limited range and isn't able to get bright enough, it's time to get it serviced or replaced. After about ten years of steady use a CRT is sure to lose some of its picture.