This International Standard describes test methods for evaluating reflection colour photographic prints with regard to changes in image appearance resulting from exposure to both low and high relative humidity. The observed changes relate to colour, tone and loss of sharpness caused by horizontal and vertical diffusion of colorants from exposure to elevated humidity levels. Other humidity-related factors, such as mould and mildew growth, and physical damage, such as curl, cockle, cracking or delamination due to humidity cycling, are outside the scope of this test method. Although the method and procedures described in this International Standard can be used to test any colour hardcopy technology, it is particularly appropriate to systems where the colorants are applied by a mechanism involving the diffusion of colorant into image-receiving layers, for example inkjet or dye diffusion processes, and to certain types of inkjet media that are susceptible to Dmin yellowing.