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For samples with low values of CIE whiteness indices, observers judged white samples much more easily and decisively than those with higher values of whiteness. The conformity between the CIE whiteness formula and the visual estimations were verified. In a study by Jafari and Amirshahi (2008), white fabrics that satisfied the CIE WI limitations were visually ranked by unskilled observers (rank ordering method) and the variations of the orders by different referees studied.
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Again, the measuring instruments must have illumination resembling daylight ( Ganz, 1979). The formulae produce relative, not absolute, white assessments seemingly adequate for commercial uses in many cases. Whiteness and tint formulae proposed by the CIE are restricted to samples differing not too broadly in tint and fluorescence. The tint deviation or hue value can still not be adequately matched. This also improves the matching of different measuring instruments for whiteness. Evaluations with the formulae are significantly improved if the sample illumination is stabilised and fitted as closely as possible to a desired illuminant.
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The CIE suggests that the formula should be used only for relative evaluations and these are valid only for measurements with a single instrument at a given time and without reference to a white scale. One clear disadvantage of CIE WI is that the system does not clarify whether the whiteness has any component of blueness or yellowness.