Gamut CIE: Stop Using This Chart!
By Chris Heinonen on
Everyone needs to stop using the Gamut CIE chart on its own. Home Theater still uses it alone. Same with Projector Central. Many other publications and websites do as well. Some might run it with a matching luminance chart, but not most. They don’t include a DeltaE chart to show errors. There is no saturations chart, and there certainly is no Color Checker chart. The worst part is many of these reviews have no idea how badly they are misleading their readers.
I’ve ranted about this before. I think the CIE chart is useful in some ways but certainly not in the vacuum that most people use it in. This was brought out again as I reviewed a new display this week and ran the gamut chart on it and then ran some more advanced measurements on it. Looking only at the gamut, we see a reasonable dE2000 error that averages below 3.0. Faced with just this chart, you might think this display is pretty accurate when it comes to color.
It is not. Now look at the Saturations chart for this same display. Instead of being uniform from 0% to 100%, we see that below 100%, everything is over-saturated. Red and Blur are the worst offenders, but on the whole the gamut has issues. The 100% values for each color are the lowest of any point. By using a chart that only shows the 100% values, readers get the impression that the colors are good but in reality 99% of colors will be bad!
The Color Checker chart simply provides more evidence of this. We can see that for this selection of common colors, not just 100% values or a grayscale, we have huge errors all over the chart. Measurements fall far from their targets, and the average dE2000 for this chart is over 7.5. We can see that Yellow is the best of any color, as those shades have the smallest dE2000 bars. On the whole, we see how misleading the gamut chart can be, and why I don’t think reviews should include it as their only evaluation of color.
Hopefully as more people switch to using CalMAN 5 and beyond, they will stop relying on the gamut chart as much. I still include it in reviews, but will drop it as the Saturations chart includes the same information, but more detailed results as well. I want to provide my readers the best information possible, even if it means using charts that others don’t and might take a bit of explanation to convey what they are saying. That’s much better than presenting a chart with information that doesn’t provide an accurate representation of the image you will see.