ASTM D2244-14 pdf free download.Standard Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates.
1.1 This practice covers the calculation, from instrumentally measured color coordinates based on daylight illumination, of color tolerances and small color differences between opaque specimens such as painted panels, plastic plaques, or textile swatches. Where it is suspected that the specimens may be metameric, that is, possess different spectral curves though visually alike in color, Practice D4O6 should be used to verify instrumcntal results. The tolerances and differences determined by these procedures are expressed in terms of approximately uniform visual color perception in CIE 1976 CIELAB opponent-color space (1),2 CMC tolerance units (2). C1E94 tolerance units (3), the D1N99 color difference formula given in DIN 6176(4). or the new CIEDE2000 color difference units (5).
1.2 For product specification, the purchaser and the seller shall agree upon the permissible color tolerance between test specimen and reference and the procedure for calculating the color tolerance. Each material and condition of use may require specific color tolerances because other appearance factors, (for example, specimen proximity, gloss, and texture), may affect the correlation between the magnitude of a measured color difference and its commercial acceptability.
3. Terminology
3.1 Terms and definitions in Terminology E284 are applicable to this practice.
3.2 Definitions of Terms Specific to This Standard:
3.2. 1 colorimeiric .speciromeier n—spectrometer, one component of which is a dispersive element (such as a prism, grating or interference filter or wedge or tunable or discrete series of monochromatic sources), that is normally capable of producing as output colorirnetric data (such as tristirnulus values and derived color coordinates or indices of appearance attributes). Additionally, the colorimetric spectrometer may also be able to report the underlying spectral data from which the colorirnetric data were derived.
3.2.1.1 Discussion—At one time, UV-VIS analytical spectrophotometers were used for colorimetric measurements. Today, while instruments intended for use in color measurements share many common components. UV-VIS analytical spectrophotometers are designed to optimize their use in chemometric quantitative analysis. which requires very precise spectral position and very narrow bandpass and moderate baseline stability. Colorimetric spectrometers are designed to optimize their use as digital simulations of the visual colorimeter or as the source of spectral and colorimetric information for computer-assisted color matching systems. Digital colorimetry allows more tolerance on the spectral scale and spectral bandwidth but demand much more stability in the radiometric scale.
3.2.2 color tolerance equation, n—a mathematical expression, derived from acceptability judgments. which distorts the metric of color space based on the coordinates in that color space, of a reference color, for the purpose of single number shade passing.
3.2.2.1 Discussion—The color tolerance equation computes a pass/fail value based on which of the pair of specimens is assigned the designation standard.” Thus, inter-changing the reference and test specimens will result in a change in the predicted level of acceptance between the specimens while the perceived difference is unchanged. A color difference equation quantifies distance in a color space using the metric of that space. Inter-changing the reference and test specimens does not change either the perceived or predicted color differences.ASTM D2244 pdf download.