Film Speed

Photographic film is categorised by its speed, which is determined by its sensitivity to light and is expressed as an ASA / ISO number. The larger the number of the film then the ‘faster’ it is. This means that the film requires less light to form an image as the film itself is more sensitive to light.

Faster films are suited to images with quickly moving objects and maintaining sharpness or dimly lit scenes where additional illumination is not desired. A slow speed film is suited to portrait photography where the subject is stationary and the lighting can be controlled. The finer silver halide grains in the slower films result in sharper detail in these circumstances.