Technical Notes
Basic Controls on a Camera
A 35 mm camera has three important controls. The lens has an aperture ring with numbers like 2, 2.8, 4, 5.6, 8, 11, etc. This ring controls the size of the hole through which the light must pass. When the dot on the ring is moved from 2 to 2.8 the light is decreased by half. When it is moved to 4 the light is cut in half again and so on for each click on the ring. These units are called f stops. The larger the number the smaller the hole.
The second control is the shutter speed dial. The numbers there are numbers like 1, 2, 4, 8, 16, 32, 64, 125, 250, 500, 1000. They indicate fractions of a second. At 125 the shutter will stay open for 1/125th of a second. The larger the number the shorter the exposure. For beginners 1/250th of a second will take care of most needs. This is fast enough to stop someone riding a bicycle. A single unit, the movement of either the aperture ring or the shutter speed dial one click has the effect of doubling or cutting in half the light.
The third control is the film speed setting. Some films react to light more rapidly than others. Every film has a speed rating on the box. There used to be ASA ratings, and now there are ISO ratings. The numbers haven't changed. The film speed is set when the roll of film is placed in the camera, either manually or automatically depending upon the camera. The other controls can be varied with each shot, but usually the film is set at its proper speed and left that way.
When a lens is focused, a certain portion of the view before the camera is in focus (sharp). One might focus on someone twenty feet away. At that point everything from fifteen to twenty five feet from the camera might be in focus while everything in front of and behind that range might be out of focus (fuzzy). This depth of field varies according to the size of the hole through which the light passes. The smaller the aperture the deeper the depth of field. In other words, faster films make it possible to use smaller apertures which allow more depth within the scene to be in focus at the same time. The aperture on most modern SLR camera lenses will remain all the way open until the moment of exposure, in order to give the viewer full light so that he can see to focus. Some cameras have a depth of field preview button which will close down the lens to the set aperture for as long as the button is pressed so that one can see how much of the scene is in focus at the set aperture.
As in the case with camera formats, a major concern with films is the degree of sharpness that they can render. This is a complex problem, but grain is usually an issue. Under magnification all films appear grainy because of the particles of silver emulsion which record the exposure to light. In general, the grain of a film gets more pronounced as the speed of the film increases. In the 1980's a new generation of films came on the market in which the grain in high speed films has been reduced, but this technology has done more to improve color negative film than slide film.
Most of the projects on which I have worked subsequent to the taking of pictures in Afghanistan have been shot on a limited number of film types. Because of the restrictions on film entering Afghanistan, and from inexperience, I used many different kinds of film on that project. It would have been much easier to begin making dye transfer prints with a project shot with only one film, but by starting with originals that had many technical difficulties and differences, I was forced to learn far more. Techniques learned while solving technical problems can be used in the future to improve already sound originals.