This International Standard describes a method for determining the intrinsic root mean square granularity (rms-granularity) of photographic films. Intrinsic rms-granularity refers to those density fluctuations produced solely by the distribution of developed image forming centres in the photographic emulsion. Continuous-tone monochrome (silver absorbing species) and colour (dye absorbing species) materials coated on a transmitting support can be measured by the procedures described in this International Standard. This International Standard is intended for imaging systems with viewing magnifications between 5× and 12× (see Annex A). The following kinds of granularity measurements are not covered by this International Standard, even though they are photographically important: — reflecting materials (photographic papers); — materials having emulsion coated on both sides of the support (e.g. some X-ray films); — the estimation of the noise power spectrum (Wiener spectrum).