Quote:
Originally Posted by

**kjgarrison**
...

I have not done a calibration with this trick of searching out the lowest dE compared to Rec709 for all the Y values but I look forward to seeing how it looks.

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One can see the numeric difference between the two calibrations by using the two spreadsheets. You can take the earlier color calculator spreadsheet, or the Accupel calculator, enter your measured xyY values and see recommendation for creating a new gamut based on these primaries. Now cut-and-paste the actual measures into the new color Y solver spreadsheet, overlaying the primary Y values and the secondary xyY values with the recommendation from the color calculator spreadsheet. This will give you a calculation of the delta E relative to the Rec709 colors, as if you had done a perfect calibration using the technique you described.

Now using the color Y solver spreadsheet, press the button to calculate the optimized values. You can see the delta E measures, again relative to Rec709, from using these Y values.

As an example, using the earlier color calculator spreadsheet, I had RGBYCM coefficients and delta E(94) of:

Code:

0.2199 0.7035 0.0767 0.9233 0.7801 0.2965
1.23 1.15 1.38 0.85 0.76 1.37

Calculating Y values using a minimization strategy yields:

Code:

0.2132 0.7133 0.0735 0.9307 0.7886 0.2876
1.06 0.94 1.20 0.79 0.66 1.10

You can see that the recommended Y coefficients differ from the Rec709 coefficients:

Code:

0.2126 0.7152 0.0722 0.9278 0.7874 0.2848
1.07 0.92 1.26 0.80 0.66 1.13

where the optimizer traded off a little more error at green to reduce the error at red and blue.

To some extent, this seems like a discussion of the number of angels on the head of a pin, as the delta E numbers in all three cases are acceptable. Still, aiming for the best target should give the best results. As the Y values do not match those calculated for a new gamut based on the primaries alone, using my tent analogy, they stretch the tent tighter over the color xy domain a little more in some places than in others, i.e., a better fit on the Rec709 primaries and secondaries may give a slightly worse fit on some of the less saturated colors. So only by trying it when calibrating a set can one decide if it looks better, the same, or a little off.

When you do get a chance to try it out on your set, let me know the results. So far, I have a data sample of one, mine. But I cannot fault Greg's logic here.