CMC Tolerancing

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CMC is not a colour space but rather a tolerancing system.

CMC tolerancing is based on CIELAB (L*C*h) and provides better agreement between visual assessment and measured colour difference. CMC tolerancing was developed by the Colour Measurement Committee of the Society of Dyers and Colourists in Great Britain and became public domain in 1988.

The CMC calculation mathematically defines an ellipsoid around the standard colour with semi-axis corresponding to hue, chroma and lightness. The ellipsoid represents the volume of acceptable colour and automatically varies in size and shape depending on the position of the colour in colour space.

The ellipsoids in the orange area of colour space are longer and narrower than the broader and rounder ones in the green area. The size and shape of the ellipsoids also change as the colour varies in chroma and/or lightness.

The CMC equation allows you to vary the overall size of the ellipsoid to better match what is visually acceptable. By varying the commercial factor (cf), the ellipsoid can be made as large or small as necessary to match visual assessment. The cf value is the tolerance, which means that if cf=1.0, then Delta E CMC less than 1.0 would pass, but more than 1.0 would fail.

Since the eye will generally accept larger differences in lightness (l) than in chroma (c), a default ratio for (l:c) is 2:1. A 2:1 ratio will allow twice as much difference in lightness as in chroma. The CMC equation allows this ratio to be adjusted to achieve better agreement with visual assessment.

Applications

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Title Application Part Number Add to quotation cart
LC 100 Spectrocolorimeter Chemicals | Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Pharmaceuticals and Cosmetics | Plastics | Sugar Solutions, Syrups and Honey | Textiles 401100
LC 100 SV 100 Kit Chemicals | Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Pharmaceuticals and Cosmetics | Plastics | Sugar Solutions, Syrups and Honey | Textiles 401120
NC45 Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Plastics | Sugar Solutions, Syrups and Honey | Textiles | Waste Water Treatment 400810
OnColor Lite Chemicals | Coatings | Household Products | Plastics | Textiles 400590
OnColor Premium Chemicals | Coatings | Household Products | Plastics | Textiles 400610
RT250 Elite Package RT 250 Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Plastics 402505
RT300 (0/45) 7 mm aperture Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Plastics 400300
RT305 (0/45) 4 mm aperture Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Plastics 400305
RT310 (0/45) 15 mm aperture Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Plastics 400310
RT320 (0/45) 4, 7 & 15 mm aperture Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Plastics 400320
RT400 (diffuse/8) 8 mm aperture Chemicals | Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Pharmaceuticals and Cosmetics | Plastics | Textiles 400400
RT500 (diffuse/8) 8 mm aperture Chemicals | Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Pharmaceuticals and Cosmetics | Plastics | Textiles 400500
RT500 Explorer Package RT500 & OnColor Lite Chemicals | Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Pharmaceuticals and Cosmetics | Plastics | Textiles 400505
RT505 (diffuse/8) 4 mm aperture Chemicals | Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Pharmaceuticals and Cosmetics | Plastics | Textiles 400504
RT520 (diffuse/8) 4 & 8 mm aperture Chemicals | Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Pharmaceuticals and Cosmetics | Plastics | Textiles 400520
RT530 (diffuse/8) 14 mm Aperture Chemicals | Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Pharmaceuticals and Cosmetics | Plastics | Textiles 400530
RT650 (diffuse/8) Compact Spectrophotometer Chemicals | Coatings | Food and Beverage | Household Products | Medical and Clinical Products | Pharmaceuticals and Cosmetics | Plastics | Textiles 407000
RT650 Expert Package RT650 & OnColor Premium Chemicals | Coatings | Food and Beverage | Household Products | Plastics | Textiles