Significato e scopo
5.1 La scala di colori CIE originale basata sui tre valori di stimolo X, Y, Z and chromaticity coordinates x, y is not visually uniform. Each subsequent color scale based on CIE values applies a weighting factor to provide a degree of uniformity so that the color differences across regions of the color space will be more comparable. D'altra parte, it is unlikely that the same color differences obtained for the same samples evaluated in different color scale systems. Evitare la confusione, comparisons should be made only when color differences or associated tolerances between samples are obtained for the same color scale system. For all colors of the specimen, there is no simple factor that can be used to precisely convert the color difference or color tolerance in one system into units of difference or tolerance in another system.

5.2 Color Difference E00 in Δ is highly recommended to use units (6) E* blood group units in the range of 0.0 to 5.0Δ. This color difference equation is applicable and widely used in industrial and commercial applications, including but not limited to automotive, rivestimenti, cosmetici, inchiostri, confezione, vernici, plastica, stampa, security and textiles.

5.3 Users of the color tolerance equation have found the addition of the three vector color difference components into a single scalar value in each system to be very useful in determining whether the sample color is within the tolerance specified by the standard. Tuttavia, in order to control for color in production, potrebbe essere necessario conoscere non solo l'entità della deviazione dallo standard, ma anche la direzione di questa deviazione. Information about the direction of small color differences can be included by listing the components determined by the three instruments for color differences.

5.4 Color tolerance selection based on instrument values should be carefully related to a visual assessment of the acceptability of hue, differenze di luminosità e saturazione ottenute utilizzando la pratica D1729. Le tre equazioni di tolleranza qui presentate sono state ampiamente testate rispetto a tali dati per i tessili e la plastica, e hanno dimostrato di essere coerenti con le valutazioni visive, within the experimental uncertainty of visual judgments. This means that the equation itself misclassifies color differences whose frequencies are no greater than those of very experienced visual color matchers.

5.5 Although color difference and color tolerance equations are commonly applied to a variety of light sources, sono stati derivati ​​o ottimizzati, o entrambi, for daylight illumination. A good correlation with visual judgment may not be obtained when calculations are performed using other light sources. The use of tolerance equations in conditions other than daylight conditions requires visual confirmation of homochromic levels according to practice D4086.

ASTM 2244-2022 “Calcolo dei limiti consentiti del colore e delle differenze di colore utilizzando le coordinate di colore strumentali”

Ambito di applicazione
1.1 This practice includes the calculation of color tolerances and small color differences between opaque specimens, such as painted panels, toppe di plastica o campioni tessili, based on color coordinates measured by an instrument based on daylight illumination. Practice D4086 should be used to verify instrumental results if it is suspected that specimens may be metamorphic, questo è, have different spectral curves despite visually similar colors. The tolerances and differences determined by these procedures are expressed in CIE 1976 CIELAB manual color space (1), 2 Unità di tolleranza CMC (2), Unità di tolleranza CIE94 (3), DIN99o color difference formula given in DIN 6176 (4), or approximately uniform visual color vision in CIEDE2000 color difference units (5).

1.2 For the Product specifications, the Buyer and the Seller shall agree on the allowable color tolerance between the specimen and the reference and the procedure for calculating the color tolerance. Specific color tolerances may be required for each material and use condition, come altri fattori di aspetto (per esempio., prossimità del campione, lucentezza, e consistenza) may affect the correlation between the size of the measured color difference and its commercial acceptability.

1.3 Questo standard non è destinato ad affrontare tutti i problemi di sicurezza, se presente, legati al suo utilizzo. È responsabilità dell'utente di questo standard stabilire la sicurezza adeguata, pratiche sanitarie e ambientali e per determinare l'applicabilità delle restrizioni normative prima dell'uso.

1.4 La presente norma internazionale è stata sviluppata in conformità con i principi di standardizzazione riconosciuti a livello internazionale stabiliti nella Decisione sui principi per lo sviluppo di norme internazionali, Linee guida e raccomandazioni emesse dal Comitato sugli ostacoli tecnici al commercio dell'Organizzazione mondiale del commercio.