What are tolerances?

WHAT ARE TOLERANCES?

NO PAIR OF SAMPLES HAS 100% IDENTICAL COLOR VALUES, AND YET SUPPLIERS HAVE TO SATISFY THE CUSTOMER'S QUALITY REQUIREMENTS FOR COLOR ACCURACY WHEN SUPPLYING PRODUCTS. WE ALSO KNOW THAT A HUMAN BEING'S PERCEPTION OF COLOR IS VERY SUBJECTIVE.

IT IS THEREFORE IMPORTANT THAT SUPPLIERS AND CUSTOMERS USE COLORIMETRY TO STIPULATE COLOR TOLERANCES, THE MAXIMUM COLOR DIFFERENCES WITHIN WHICH PRODUCTS WILL STILL BE ACCEPTED.

COLOR TOLERANCES CAN BE ESTABLISHED IN ALL COLOR SYSTEMS, INCLUDING THE CIE XYY SYSTEM OR THE CIELAB SYSTEM, WHICH IS THE ONE MOST FREQUENTLY USED. HOWEVER, THE DISADVANTAGE OF THE TRADITIONAL SYSTEMS IS THAT VISUALLY THESE DO NOT HAVE EQUIDISTANT SPACING. WHAT DOES THIS MEAN? IN THE CIELAB SYSTEM, FOR EXAMPLE, YOU COULD ESTABLISH THAT A MAXIMUM COLOR DIFFERENCE OF DE*=1 IS ACCEPTABLE. HOWEVER, WHEN ASSESSING VARIOUS PAIRS OF COLORED SAMPLES WITH A MEASURED COLOR DIFFERENCE OF DE*=1, YOU FIND THAT DE*=1 MAY WELL BE AN ACCEPTABLE COLOR DIFFERENCE WITH BRILLIANT YELLOW OR GREEN TONES, BUT WITH ACHROMATIC, GRAY COLORS DE*=1 REPRESENTS ANOTHER, UNACCEPTABLE COLOR. THE SAME MATHEMATICAL DIFFERENCE OF 1 DOES NOT THEREFORE CORRESPOND TO OUR VISUAL PERCEPTION.

SEVERAL NEW TOLERANCE FORMULAS HAVE BEEN DEVELOPED IN ORDER TO AVOID HAVING TO ESTABLISH DIFFERENT COLOR TOLERANCES IN THE CIELAB SYSTEM FOR EVERY COLOR. THESE FORMULAS CORRECT THE NON-EQUIDISTANT SPACING OF THE CIELAB SYSTEM. TODAY THE MOST COMMON PUBLISHED TOLERANCE FORMULAS ARE THE CMC AND THE CIE-94 FORMULAS. HOWEVER, THESE ARE MORE OFTEN BEING REPLACED BY MORE RECENT TRANSFORMATIONS SUCH AS DIN99 OR CIEDE2000.