Photo Journalism 4(1+3)

Lesson 15 : Processing of Film in Conventional Photography

Film Developing

A photographic film is simply a sheet of plastic coated with a silver halide emulsion. The silver Halide emulsion contains silver halide salts that are bonded by gelatin. A regular photographic film used for black and white photography is made up of the following components:

1. The Base: The base of the film is made up of cellulose acetate and can be transparent, translucent or even opaque. The primary function of the base is to support the emulsion in place.

2. The Emulsion: The emulsion layer is a thin layer of gelatin containing the light-sensitive silver halide salt crystals. The size of the halide crystals determine the sensitivity, contrast and resolution of the film.

3. The Anti-halation Backing: The anti-halation backing layer is primarily a part of the photographic film to prevent reflection of light from the base into the emulsion.

4. The Overcoating: The overcoating layer is a clear, protective sheath made of gelatin that protects the film from physical damage like scratches or abrasions before development.

5. The Noncurl Coating: The hardened gelatin layer applied to the back of the film is called the non-curl coating. Since the emulsion swells when it is wet and shrinks when it becomes dry, there is a resulting strain on the flexible film base, which can result in curling. The non-curl coating prevents this curling.