Colorimetric Limit
Ellipsoidal tolerance boundaries calculated around a target color standard provide a mathematically consistent method for determining acceptable shade variation in finished textiles. The delta E CMC tolerance uses a modified color difference formula that adjusts the acceptability region based on the position of the standard in color space. Human sensitivity to differences in chroma, lightness and hue varies depending on how saturated or bright the sample is.
By scaling the tolerance ellipse, this formula aligns the digital pass-fail decisions with visual assessments.
Mathematical Basis
Numerical weights for lightness and chroma define the shape and size of the boundary ellipse. For most apparel fabrics, the ratio of two to one is used to allow more variation in lightness than in chroma. The resulting delta E CMC tolerance value must be below a specified threshold, often set at one point zero or lower for critical components.
This ratio ensures that the fabric is judged against realistic human visual limits.
Industrial Standard
Spectrophotometric measurement of the production batch provides the input data for this evaluation. Technicians scan the fabric at multiple points to generate an average reflectance curve. If the calculated color difference exceeds the delta E CMC tolerance, the software flags the lot for rejection or re-dyeing.
Quality Decision
Garment factories specify this tolerance in their supply contracts to ensure that panels cut from different rolls match when assembled.
