Application: How To Adjust Levels
Hopefully, all of this talk of science and theory is inspiring you to try calibrating your own display. If you have the basic tools available, you can do this by following the steps we’ll outline in the next four pages. As stated in the beginning, you’ll be adjusting the monitor’s controls only. This method does not use a software look-up table. You can also create an ICC profile for use with your graphics apps. We’ll show you how on page nine.
We suggest you follow the steps here in the order we give them. Since there are nearly always interactions between controls, this procedure minimizes the need to go back and forth to dial in your display.
First, you should go through a little pre-flight drill.
- Warm up your monitor for at least 30 minutes before you start. That way, the backlight will be stable and you’ll get the most accurate measurements.
- Find a picture mode that is neither too bright nor too dark. Usually one marked Standard is a good bet.
- Set the Color Temp to User or Custom so you have access to the RGB sliders.
- If there is a Gamma preset, choose 2.2.
- Now you’re ready to begin.
First up are the level adjustments; Brightness and Contrast. These can be set by using a couple of test patterns. There are many available that will work. Here are a couple of samples.
This is one of the grayscale step patterns generated by our Accupel. You can also find this pattern online. In fact, we downloaded this very graphic. You should see 11 brightness steps. Fifty percent is in the middle.
Here is a PLUGE pattern.
PLUGE is a traditional term for patterns used to set levels. The acronym stands for Picture Line Up Generating Equipment. Definitely a throwback to the analog era! You should be able to see four vertical bars in the center of the field. They start with the darkest on the left and become brighter as you go right.
This pattern is good for setting contrast.
We’ll explain how to use all of these patterns in a moment. The important part is the section on the right side. There are a total of 33 bars ranging from 0 to 100 percent, or in RGB terms, 0 to 255.
Finally, we have another pattern that’s even better for setting contrast.
In this pattern, you should see eight concentric squares that vary in brightness. If you can’t see all eight squares, that color is clipping.
The common theme in all of the patterns is that they have bars a few brightness steps apart from one another. By viewing these bars, it’s easy to see when you’ve set the controls too far in one direction because one or more of them blend together. This is what we mean when we use the term clipping.
Start with the first pattern, the grayscale steps. Lower the Brightness control until the darkest two bars become one. On most monitors, they’ll never actually blend because they’re quite far apart in brightness.
Now try the same exercise with the second pattern. On some monitors, the darkest bar will disappear. When this happens, turn Brightness back up until the bar is just visible. If you can turn your Brightness control all the way down without clipping any bars, then you should set the control with a meter instead. Display a 100 percent window pattern like this one.
Measure the window with your meter and adjust brightness until it’s at the value you want. We always use 200 cd/m2 but your preference may vary based on your room lighting conditions.
Now display the third pattern. Raise the Contrast control until the rightmost two bars blend together. That’s your clipping point. If you can raise it all the way and the bars are still visible, try the fourth pattern with the colored squares. This one is more precise because you can see the clipping point of each primary color. If one color clips, you’ll lose grayscale accuracy because the monitor has literally “run out” of that color. We’ve noted in all our monitor reviews that the Contrast control’s default setting is usually at its highest possible point. Raising it even one click often clips at least one color and sometimes all of them.
This is pretty easy to do, even without a meter. Most monitors will let you set the brightness anywhere in their range without clipping blacks. You just have to decide how bright you want your screen to be for your particular workspace. And contrast is generally fine at its default setting.
Since the final values of your level adjustments determine the measurement parameters for gamma, it’s important to do this step first. As we’ve already demonstrated, poor gamma has an obvious negative impact on image quality.