This document describes test equipment and procedures for measuring the light stability of photographic prints when subjected to a filtered xenon-arc light source at specified levels of illuminance (irradiance), temperature and relative humidity. It is applicable to both colour and monochrome reflection prints, transparent films, or translucent films. It is also applicable to photographic prints in general, photobooks, or prints for backlit displays.

General indoor display conditions described herein are intended to simulate common use conditions found in houses, apartments and other dwelling places where indirect lighting due to filtering (through window glass) and shading is often the principal illumination causing displayed photographs to fade.

Simulated in-window display conditions are intended to simulate terrestrial daylight transmitted through standard architectural window glass (double glazing). A typical example of such display can be found when images are displayed in store windows, facing toward the outdoors, so that they can be viewed by people outside of the store^[5][6].

NOTE 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 the stability of the image itself, will determine the useful life of a print material.

General guidance is given in ISO 18937-1.