This part of ISO 787 describes photometric methods of test for comparing in the visible spectrum a) the tinting strength of two similar (see note 1 ) coloured pigments dispersed in an alkyd resin without a drier; b) the scattering power of two white pigments of the same type dispersed in an alkyd resin without a drier. These methods of test provide an instrumental alternative to those described in ISO 787/16 and ISO 787/17 respectively, avoiding the necessity of visual matching. NOTES 1 This International Standard is not appropriate for the comparison of coloured pigments that on reduction differ greatly in colour. 2 When one of these general methods is applicable to a given pigment, only a cross-reference to the appropriate method should be included in the International Standard relating to that pigment, indicating any detailed modification which may be needed in view of the special properties of the product in question. Only when the appropriate method in this part of ISO 787 is not applicable to a particular product should different photometric methods for determination of relative tinting strength and determination of relative scattering power be specified.