Application: How To Adjust Color
We always measure color gamut and luminance in our monitor reviews, even though those parameters are not adjustable in most cases. To do this, you would need a color management system (CMS), and that is just not available on many displays. In fact, our only experience with this feature is from a few high-end projectors and TVs. If you have color gamut presets, they can help you achieve more accurate color. Choose the one that most closely matches your task (sRGB/Rec. 709 for most situations or Adobe RGB 1998 for photo editing). Then measure to see if it indeed meets the spec.
Let’s go through a brief anatomy lesson.
Here is the chart you’ve seen in all our monitor reviews. This one is from an AOC Q2963PM. At the top is the saturation sweep. The color saturation level is simply the distance from the white point on the CIE chart. You can see the targets moving out from white in a straight line towards each primary and secondary color. The farther a point is from center, the greater the saturation until you hit 100 percent at the edge of the gamut triangle. Rather than just measuring the 100-percent saturation level, we measure 20, 40, 60, and 80 percent too. Many monitors can generate a good-looking chart if only the 100-percent saturation is measured. This is a much more precise way of measuring color gamut.
The middle portion of the chart shows gamut luminance. This is the third dimension to color that is not shown on the CIE chart. We believe this has a greater impact on perceived color accuracy than the points on the gamut triangle. The shorter bars mean better performance. This monitor is superb.
The bottom chart is the Delta E information. Again, scoring below three means the error is not visible. Our chart shows the errors for each color, at each saturation level.
If you have one of the very rare displays with a color management system, we’ll give you a brief rundown of how to adjust it. Bear in mind that no two systems are quite the same, and some don’t work properly. Any use of a CMS should be done carefully, with instruments, and with the understanding that it may not actually improve your monitor.
A traditional CMS has three adjustments for each primary and secondary color: Hue, Saturation, and Lightness. Obviously, each one has a different effect. Let’s look at a blank CIE chart once again.
When you adjust the hue for green, for example, it moves that color point either towards cyan or towards yellow. If you adjust the hue of a secondary color, it moves closer to one of the primaries that make it up. For example, magenta moves between blue and red.
Adjusting saturation moves the color closer to, or further from, the gamut triangle. Just like our bulls-eye chart for adjusting grayscale, you can manipulate the hue and saturation controls to bring a color point into the target square.
Now let’s consider the lightness control.
In a CMS, lightness is just another term for luminance. To adjust this, you dial in the color points to the CIE chart first. Then, starting with red, adjust lightness until the bars pictured above are as close to zero as possible. It sounds simple, and it can be. The likelihood is that all three controls will interact and you’ll have to go back and forth until you get the best result. Adjusting a CMS can be very time-consuming. The basic procedure, however, involves adjusting hue and saturation for each color, and then going back to adjust lightness.
Creating An ICC Profile
Most monitors have chromaticity data embedded in their firmware, but this assumes it was measured correctly at the factory. And we know from experience no two monitors are identical. The best way to create an ICC profile is to measure the primaries yourself. We use QuickMonitorProfile, a free download, to do this for our reviews.
Once you’ve gathered the CIE coordinates for each primary color, you have everything you need to create the profile. All you need to do is select Custom in the Chromaticity coordinates drop-down, and then enter the x and y values for each color. Once you save it, you can call it up at any time in the future.