We would like to see how accurate our method for conversion of nonlinear RGB values  to XYZ space really is. The best way to compare values is by converting to another coordinate system, CIEL*a*b* space, and taking the deltaE values between two sets of data.

            The standard deltaE measurement is for deltaEab. This measurement, however, is not always accurate because there are non-uniformites in the CIEL*a*b* color space. The Society of Dyers and Colourists Colour Measurement Committee (CMC) created another deltaE measurement that attempts to allow for the non-uniformity of CIEL*a*b*. deltaEcmc is now the British Standard, and is used by the researchers of the VASARI project for their color measurement. For our project, we will calculate both the deltaEab and deltaEcmc values.

            We have created two sets of test values. The first is a series of nine greyscale swatches that will focus on our gamma correction. The second is a series of four color swatches that will test our RGB to XYZ conversion.

            We have measured the XYZ values of both test sets with the spectroradiometer and converted  these values to L*a*b* space. We have also taken images using our digital camera of each test swatch and performed the sequence of conversions to arrive in L*a*b* space for each of these.
            The function to find the deltaE values is getdeltaE.m.

            For the nine greyscale swatches, these are the deltaE values:

deltaEab:      15.5463   13.8849    6.9301    6.9816    1.9650    5.1708    3.9814    9.7647    11.2890
deltaEcmc:   12.9416   12.8941    5.3496    6.3054    2.2713    4.6286    4.7064    12.0494  12.2568

           For the four color swatches, these are the deltaE values:

deltaEab:      5.5881   11.9809   10.9431    3.1384
deltaEcmc:   4.1676    8.3506     8.2649     3.1151