Creating a black-and-white photo
Creatinga black-and-white photo is essentially a three-step process: The first two steps (taking the picture and developing the film) produce a negative; the third step (enlarging) produces a print.
Taking the picture
Light – whether it’s radiating from the sun or comes from a lamp or flashlight – illuminates the subject and is in turn reflected by it into the lens of the camera.
The lens gathers the light that strikes it and forms an image of the subject, and projects this image onto the film.
The film (more precisely, the light-sensitive coating of the film, the emulsion), within certain limits, responds proportionally to the light which is transmitted by the lens. A chemical reaction takes place between the incident light and the light-sensitive silver salts (halides) imbedded in the emulsion as a result of which a latent, i.e., invisible, image of the subject is formed on the film.
Development of the Film
Development turns the latent image into a visible one, the active ingredients of the developer converting the light-struck silver salts into metallic silver more or less in proportion to the exposure which they received. The result is an image of the subject in which the values of light and dark are reversed: Subject areas that were comparatively light (and reflected a correspondingly large amount of light onto‘ the film) appear relatively dense and black, whereas the darker or more shaded areas of the subject, which reflected less light, appear proportionally lighter and more transparent.
The film has become a negative.
To prevent those light-sensitive silver salts which received only little exposure or none at all from turning black, too, the moment the de~ veloped film is exposed to light (which, of course, would destroy the image), the negative must subsequently be made insensitive to light by treating it in a fixer solution. And to make it permanent, it must be freed from all processing chemicals by washing before it can finally be dried.
Printing the Negative
Printing once more reverses the tonal values of the image. The negative is made to yield a positive picture on paper in which the shades of light and dark correspond more or less to those of the photographed subject. This operation takes place in the darkroom by shining light through the negative onto a sheet of light-sensitive paper. As with the film the wxposed paper must be developed, fixed and washed.