ISO 3668-2017 pdf free download

ISO 3668-2017 pdf free download.Paints and varnishes Visual comparison of colour of paints
Peintures et vernis — Corn paraison visuelle de ía couleur des pein tures.
5.1 General
The quality of natural daylight is variable and observers’ judgements are likely to be affected by nearby coloured 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 strongly coloured surfaces, other than panels under test, shall be permitted in the field otview.
5.2 Artificial illumination by means of a colour matching booth
The colour matching booth shall be an enclosure from which external light is excluded and which is illuminated by a light source giving a spectral power distribution falling on the test panel, approximating to that of CIE standard liluminant D65, CIE standard llluminant A (as specified in ISO 11664-2) or CIE ifluminant FL 11 (as specified in CIE 15.3).
Where a light source having a different spectral distribution is used, it shall be agreed by the Interested parties.
The quality of simulation of daylight shall be assessed by the CIE method specified In CIE Publication No. 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 4000 lx, a figure towards the upper end of the range being desirable for dark colours.
The interior of the colour-matching booth for general use shall be painted a matt neutral grey (the amount of a and b’ should be less than 10) with a lightness L of about 45 to 55. However, when mainly light colours and near white colours are to be compared, the interior of the booth may be painted so as to have a lightness L* of about 65 or higher in order to give a lower brightness contrast with the colour to be examined; when mainly dark colours are to be compared, the interior of the booth may be painted rnatt black with a lightness L of about 25.
NOTE L’, ci and b refer to the CIELAB System (see ISO 11664-4).ISO 3668-2017 pdf free download.