Originally Posted by XBR11
I do not even pretend to know what these charts mean, but I'm guessing that the third chart is the best of the three, what with the top color lines all matching and flat, and the bottom purple line on the bottom and flat.
What % improvement do you guess the final one is over the D-Nice offsets? Like does the picture look 10% better now? 25%?
A very brief, low-tech explanation of how to read the the charts:
1. The upper half of each chart shows the level of the individual primary colors (red, green, and blue) from black (0%) to white (100%) -- the horizontal axis.
2. The 100% level on the vertical axis represents the grayscale color temperature that we want to obtain. In our case, it is the film and TV standard called D65 -- google it.
3. The object, as you correctly deduced, is to get the red, green, and blue lines to be as close to the 100% level as possible. Ideally they would all fall on a straight horizontal line.
4. The lower half of each chart shows the deviation of the colors from the desired 100% D65 level. (The mathematical relationship is not obvious so don't try adding or subtracting values from the RGB curves above.)
5. The vertical axis of this violet curve represents the deviation from a perfect match. It is called "delta E." In mathematics, the Greek letter delta is used to signify "difference." The letter "E" stands for the quantitative value of the deviation.
6. Some say that a delta E of three or greater can be seen by the human eye. Others say that a more stringent delta E of one or below is needed to be imperceptible.
From the charts you can see that the factory settings are not that good. They show that the grayscale is too bluish green and the delta E is always greater than about seven. After applying the offsets from D-Nice, the RGB curves are closer together and the resulting delta E, for from about 15% gray to white, is always below six. At a few points, delta E is at the critical value of three. This indicates a noticeable improvement in the grayscale. After performing a true grayscale calibration, the RGB curves track each other quite well. The delta E is below two for most of the grayscale range -- from black to white.
There is no way to express the improvement in the way you asked. Applying the offsets results in a visible improvement in grayscale and that's about all I can say.
I hope this helps you.