I used a KODAK IT8.7/2 Q-60E1 target for determining the gamut range of the scanner. The data from the scanned target were calculated by a special program and represented as the following diagram:
To build the next diagram I found the difference between the colors of the original target and the scan. The Color Difference value should not exceed 5.0 or the color discrepancies become visible for a majority of people.
The closer to the X axis, the better