This International Standard describes test equipment and test procedures for determining the colour stability of photographic colour images when subjected to outdoor conditions. It does not specify limits of acceptability or failure criteria. Instead, it provides means for measuring image changes that take place during the aging of pictorial photographic images and indicates the critical image-change parameters that should be reported. Users of this International Standard should determine which test end-points best simulate the intended display application. This International Standard is applicable to pictorial images made with digital printing media, for example: — prints on coated papers, coated and uncoated clear and opaque films, vinyl, polyester, synthetic papers and other plastic substrates, laminated and not laminated; — dye-based and pigment-based inkjet prints with aqueous, solvent, phase-change, or UV curing inks; — thermal dye and mass transfer; — dye sublimation prints; — digitally-printed dye-diffusion-transfer prints; — liquid- and dry-toner xerographic prints; — liquid toner electrostatic prints; — digitally printed images made with traditional chromogenic and silver dye-bleach photographic materials; — colour direct thermal prints. In these digital printing processes, the ink laydown is controlled by means of digital pixel information, and all of the settings and controls of the printing system can be documented and repeated. In contrast, for many analogue printing systems, the control over the ink film thickness can be subject to manual adjustment. Window graphics on the outside of windows are covered by this International Standard. Window graphics on the inside of windows, for which sunlight is filtered by a layer of glass, will be covered by ISO 18937. This International Standard does not include test procedures for physical stability of images, supports or binder materials. However, it is recognized that in some instances physical degradation such as support embrittlement, image layer cracking, or delamination of an image layer from its support, rather than image stability, will determine the useful life of a print material. NOTE Image print stability results determined for one printer model, ink set, printing mode, print resolution and media combination are not applicable to image prints produced through another printer model, ink set, printing mode, print resolution and media combination, even if the ink jet cartridges and/or media used in testing are the same.