Developing and Editing Film
Remember great-grandma’s old silverware that was actually made of silver and how it tarnished? The reason it tarnished was because silver blackens when exposed to light and oxygen. Black and white film and processing uses this principle to create visual images. Finely ground silver particles were placed into an emulsion that was applied to a clear backing layer, originally glass but eventually plastic.
A camera’s lens projects the light reflected from an image onto the light sensitive film.
Bright areas of a scene such as white reflect a lot of light so that area of the film will “tarnish” more and turn black. Black areas reflect little light so those areas would remain clear. This is the basis of how a negative image is created.
Film is processed by submersing it in several solutions. The first solution is called developer.
After the appropriate amount of time in the developer the film is moved to a solution known as stop bath. Once the stop bath has done its job the film is moved to a solution known as fixer. The fixer removes any silver particles that have not tarnished and turned black creating the finished product which is now a negative image.
The film with its newly created negatives is then thoroughly washed to flush away all the processing chemicals and then dried.
In the darkroom light is projected through the negative onto photographic paper.
Photographic paper uses essentially the same emulsion as photographic film which is now applied to white paper rather than clear plastic.
White areas of the original scene caused the film to darken creating black areas of the negative. No light strikes the paper in these areas because the black portion of the negative blocks it. In these areas the paper remains white. Black areas of the original scene didn’t cause the film to darken thus remaining clear. Light does travel through these areas of the negative striking the paper causing the silver in the paper’s emulsion to blacken.
The paper is processed in the same way as the film, reversing the process and revealing the original scene.