I CALIBRATED WITH COLOR BARS; ISN’T THAT ENOUGH?
The simple answer is "no," although color bar adjustments are a key part of monitor calibration, and we should all be performing them in the field. SMPTE and ARIB color bars are often used for calibration because they can quickly tell you a lot about your image and make adjusting it fairly easy. They can help you adjust brightness, contrast, saturation and phase. Not too shabby.Brightness and contrast can be adjusted by looking at two regions of your bars. To get the black levels correct, adjust the monitor brightness. To do this, look at the PLUGE (picture lineup generation equipment), which is a small grayscale in the bars pattern. This grayscale includes bars that are darker than a legal zero black level, ones that are at zero black level and bars that are brighter than black.
The idea here is to change the brightness of your monitor until the darker-than-black bar isn’t visible, right along with the fully black bar next to it. The bar next to that, which is slightly brighter than black, should remain just barely visible.
Now, we’ll use contrast to adjust our white level, which is a bit trickier. It involves looking at the 100% white bar (the bar that shows at 100% on a waveform) on your monitor and making it just the right brightness. You can measure the brightness of the monitor in foot-lamberts (fL) and adjust it based on your monitor type. SMPTE specifies 35 fL, ideally. However, this varies greatly by the viewing environment and monitor technology, so a general rule of thumb is to adjust the contrast in your viewing environment until the white bar gets as bright as possible without causing a cast (or yellowing) on neighboring color bars. By adjusting both white and black levels, we can feel good about using the monitor for exposure overall.
It’s important to realize these adjustments are specific to your viewing environment. A monitor in a dark room will need very different levels than one being used outside during the day.