Essentially modern computer monitors assume that the video card is going to produce a consistent signal that is exactly to spec. Modern computer monitors almost never need brightness calibration, and a lot of LCD monitors either don’t have a control labeled "brightness" or have one that controls the backlight brightness, which is a completely different adjustment.
One question we get a lot is, "why does the brightness control need to be calibrated? Isn’t there a standard voltage or code value for black that can be locked in at the factory?" This isn’t a dumb question at all. Once black level is set properly you can move the white level up and down without changing the black level by adjusting the "contrast" control, but we’ll save that for another article. So when you move the black level up by raising the brightness control, you’re also moving the white level (and every gray level) up at the same time. You’re adding or subtracting a constant amount from every brightness level on the display. You move the black level up or down, and every other level as well. When you move the brightness control up and down, you’re in effect sliding the range that your display will handle up and down. The reason it’s called "brightness" and not "black level" is that when you change the setting you’re not just moving the black level. If the input is digital (such as DVI or HDMI), then you’re setting a digital value that will be considered black. If the input is analog (such as component or VGA), then you’re setting a voltage level that the display will consider black. What you’re really setting is the input level that the display will consider absolute black. Professional video engineers refer to "black level," which is more descriptive. The name "brightness" is really not a very good one. If you just want to know how to use your test pattern disc to adjust your brightness control, skip ahead to the section called "Using the PLUGE Pattern."
If you want to know why brightness needs adjustment, what’s really going on when you move the brightness control, and how different kinds of brightness adjustment patterns work, then read on. We’re going to talk about how to set brightness correctly, but first we want to take some time to talk about some of the history and background of the brightness control. If brightness is set too high, the image contrast goes down and the picture loses its "snap." It really needs to be set first, and if it’s done right it should stay right throughout the rest of the calibration process. If brightness is set too low, the dark parts of the image are lost completely. Of all the settings on the display, the brightness control is probably the most important. Material from Spears & Munsil with permission.
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