When deciding which colour difference calculation to use, consider the following rules

  • Select a single method of calculation and use it consistently.
  • Always specify exactly the equation used, illuminant and observer. Model of instrument used should also be specified.
  • Never attempt to convert between colour differences calculated by different equations through the use of average factors.
  • Use calculated colour differences only as a first approximation in setting tolerances, until they can be confirmed by visual judgments.