The fundamentals of photography

Black and white photography can produce beautiful, artistic images. However, what happens to your film when you take a picture? And, why is it necessary to develop film? There are essential steps that you must take to produce a negative, and most of it has to do with science.

A black and white photographic negative is the reverse image captured on your film when it is exposed to light, and then developed. What you see on a negative is the opposite of what you originally took a picture of: the lightest areas of your scene will be the darkest on the negative, and the darkest areas in your scene will be the lightest on the negative.

How does this happen? It starts when you take a photo. Light strikes the light-sensitive coating on your film and creates an image. Your film is a plastic strip, which is coated with light-sensitive silver halide crystals that float in a hardened gelatin. Light causes an electrochemical reaction on the silver halide crystals in the emulsion. Only those silver halide crystals hit by light will be altered. The light from your scene actually changes the electrical charge in each silver halide crystal, making an invisible image, or latent image, that is sensitive to film developer (a chemical used to develop film).

Film is very sensitive to both time and temperature when developing. Developing your film for too long, not long enough, or at the wrong temperature can affect a negative's appearance by changing the negative's density and contrast. A high-contrast negative has very dense highlights and very thin shadows. A low-contrast negative has very little difference between the density of the highlights and the shadows.

How does this happen? The emulsion layer of your film contains many silver halide crystals both above and below the surface of the emulsion. As more light exposes your film, the amount and depth of the exposed crystals increases. The longer film developer is developing your film the more deeply it soaks into the emulsion and changes more of the silver halide crystals into dark metallic silver. Therefore, the longer the developing time, the more the dark metallic silver builds up, creating a denser and more contrast-filled negative. This creates an overdeveloped negative. On the other hand, the less developing time you give your film, the less chance the developer has to soak into the emulsion. This leaves you with less dark metallic silver on your negative. This negative is underdeveloped.

The temperature of your film developer is also important. If the developer is too hot it can melt the gelatin holding the silver halides on your film. An example is Jell-O. Jell-O is mostly gelatin and is a liquid when hot and a solid when cooled. If on the other hand, the temperature of your film developer is too cold, the gelatin will not accept the developer as effectively because the gelatin is more similar to the solid Jell-O.

There are other steps to film developing that are also necessary to complete the process of film development. When you want your film to stop developing a "stop bath" is used to stop the developer. This can be plain water or a very mild acetic acid bath. The next step is called fixer. This chemical renders the film insensitive to light. When fixing is complete, you can view your negatives in light. The final step is to wash your film in water. The wash works to remove all left over chemicals.

There's a lot of science involved when developing your black and white film. By understanding what happens during film exposure and the developing process, and carefully performing each step correctly, it will be much easier to print your negatives and create a work of art!

DENSITY is the thickness of the dark metallic silver that builds up on a negative during film development. CONTRAST is the difference between the dense areas on your film and the are HIGHLIGHTS which are the brightest parts of your scene. Thin areas on your film are SHADOWS which are the darkest of your scene.

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