Black & White Film Characteristics

Black and white photographic film is a very light sensitive material and consists of an imaging layer that contains sub micron sized grains of silver halide crystals that act as photon (light) detectors. When the crystals are exposed to light they undergo a photochemical reaction. Photographic film is categorised by its speed which is determined by it sensitivity to light and is expressed as an ASA / ISO number. The higher the number of the film then the ‘faster’ it is. This means that the film needs less light to form an image, as the film itself is more sensitive to light.

Faster films are suited to taking photographs of quickly moving objects and maintaining sharpness or when taking pictures in dimly lit surroundings without the benefit of additional illumination such as a flash. Although increased light sensitivity is achieved by larger silver halide grains and these can result in a blotchy or ‘grainy’ picture.

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 produce better results for these purposes.

In comparison with colour films, there is a wider range of film speeds available for black and white films. Therefore in particularly low available light conditions it is possible to use a film that is perfectly suited to that environment. Commonly known manufacturers of black & white film include Ilford, Kodak, Fuji and Agfapan and within these brands there are a range of film speeds. Within this module, I have mainly used HP Ilford films such as Ilford PanF Plus (ISO 50), Ilford FP4 Plus (ISO 125) and Ilford HP5 (ISO 400).