FAQ: “Why do my hand calculated L* a* b* values not match the values displayed in EasyMatch QC?”
Usually the difference between hand calculated and software calculated values is very small. The ColorCalculator (in the EasyMatch QC software) carries calculations to double precision. This means that every calculation within the software is carried out to about 15 decimal places until the final value is displayed. When the final value is displayed, it is rounded to 2 decimal places. In hand calculations, X Y Z values can only be displayed to four decimal places. So in summary, the difference between hand calculated and sftware calculated values is a rounding difference.