Graininess and Granularity are terms used to represent a different aspect of the grains. Granularity is a physical measurement and graininess is a subjective sensation. To make it easier for our readers, our site shall use granularity to represent the fine grain measurement of film, and graininess to represent the grain condition of photo.

If the negative image is made of fine grains, it can be enlarged to about 20 times and still remains a good quality. If it is made of coarse grains, the enlargement may be limited to less than 10 times for an acceptable print. Of course, there is no universal rule to fix the size of prints, however, organizers of competition etc. will have their own requirement. In comparison, even at the size of 3R, we can find the difference between fine and coarse grain. Except for news photo, we all treasure the snapshot of a great event rather than its graininess. In general, most of us are not photojournalists, graininess is the most important part of our photos.

The sensitive emulsion of film is made of Silver Halide, the Halide family includes Silver Bromide, Silver Chloride and Silver Iodide. Since the chemical reaction of Silver Bromide is better, and the grains produced have a cold black tone, nearly all films use Silver Bromide for the senstive emulsion. But due to the cost is higher, silver iodide is used for some photographic paper. The whole sensitive and developing (reducing) reaction is in fact based on the actinic effect that generated negative charge in the halides. With the reducing agent of developer, the silver grain will be separated from its chemical bond, into chemical silver, black in color. With different density of silver grains, they form the final image. Chemical silver can be converted into its metallic state by electrolytic process.

Grains of silver reduced will bind together with one another, the minimum is four atoms, in general it is usually a lot more. This is affected by the quality of emulsion, sensitivity, exposure, developer, temperature, agitation and processing technique etc. The sensitive element of color film is still silver halide and will be replaced by color dye during processing. Color dyes will form around silver grain, and with three layers of dye, color film is usually coarser than B/W film.