Tony, how much grey is grey?

Very good question! Like Genixia said, it's supposed to help prevent phosphor burn, so ideally it should depend on the average sample of the programming in the middle of the screen.

However, I know that's not practical to do in a lot of applications. Heck, even my Mitsubishi TV set, which has its own gray-bar system built in, doesn't alter the gray level dynamically. It's a flat setting from the factory. It is, however, settable in the service menus if you know the secret handshake to get into the eeprom. I do not know what IRE level the gray is, but it looks close to 50 percent.

If this question is really important to you, I could use my Avia calibration disc to find out the IRE level exactly.

You could, theoretically, take an average sample of the programming content that's currently on the air and decide what your gray level should be based on that. The problem is that someone who watches a lot of X-files would need a different value than the people who watch a lot of South Park. So you can't win.

Also note something cool that my Mits TV set does: When it's doing the gray pillar bars, the horizontal position of the image and the bars varies slowly over time by a few percent. So that even if there is some slight burn because of the difference in the amount of gray, the edges of the bars don't burn into a perfect vertical line. It doesn't move while you're watching it, so it's not irritating, it just changes each time you power on the TV and only changes slightly each time.

My Samsung high def satellite receiver seems to use about the same level of gray for its pillar bars that my Mits TV uses. It does not, however, vary the position like the TV does.