EN ISO 3668-2020 pdf free.Paints and varnishes — Visual comparison of colour ofpaints.
This document specifies a method for the visual comparison of the colour of films of paints or relatedproducts against a standard (either a reference standard or a freshly prepared standard) using artificiallight sources in a standard booth.
lt is not applicable to coatings containing special-effect pigments, e.g. metallic, without previousagreement on all details of illuminating and viewing conditions.The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document. For dated references,only the edition cited applies. Forundated references, the latest edition of the referenced document (including any amendments) applies.ISO 1514, Paints and varnishes —Standard panels for testing.
ISO 3270, Paints and varnishes and their raw materials —Temperatures and humidities for conditioningand testing.
ISO 11664-2,Colorimetry – Part 2: CIE standard illuminants.
ISO 18314-1,Analytical colorimetry — Part 1: Practical colour measurement.
ISO 23603,Standard method of assessing the spectral quality of daylight simulators for visual appraisaland measurement of colour.
CIE 15.3,Colorimetry.
CIE 51.2,A method for assessing the quality of daylight simulators for colorimetry.
The colours of the paint films to be compared are observed under specified illumination and viewingconditions, using a colour matching booth. For the expression of colour difference components (hue,chroma and lightness) a procedure is described, i.e. description by using a particular rating schemeAssessment of metamerism is also taken into account.
The quality of natural daylight is variable and observers’ judgements are likely to be affected by nearbycoloured objects.For referee purposes, therefore, closely controlled artificial illumination in a colour-matching booth shall be used. The observer shall wear clothing of a neutral colour and no stronglycoloured surfaces, other than panels under test, shall be permitted in the field of view.
The colour matching booth shall be an enclosure from which external light is excluded and which isilluminated by a light source giving a spectral power distribution falling on the test panel, approximatingto that of ClE standard lluminant D65,CIE standard lluminant A (as specified in ISO 11664-2) or CIEilluminant FL11 (as specified in CIE 15.3).
Where a light source having a different spectral distribution is used, it shall be agreed by the interestedparties.
The quality of simulation of daylight shall be assessed by the ClE method specified in ClE PublicationNo.51.2 and ISO 23603.The spectral distribution of the illuminant shall be in category BC(CIELAB)or better.
The level of illumination at the colour-matching position shall be between 1 000 lx and 4 000 lx, a figuretowards the upper end of the range being desirable for dark colours.EN ISO 3668 pdf download.