The Film Camera

Camera Basics A still film camera is made of three basic elements: an optical element (the lens), a chemical element (the film) and a mechanical element (the camera body itself).

The Lens At its simplest, a lens is just a curved piece of glass or plastic. Its job is to take the beams of light bouncing off of an object and redirect them so they come together to form a real image – an image that looks just like the scene in front of the lens.

Focusing the Lens To focus the image, move the magnifying glass closer or farther away from the image This is what you're doing when you turn the lens of a camera to focus it -- you're moving it closer or farther away from the film surface. As you move the lens, you can line up the focused real image of an object so it falls directly on the film surface.

Photons- Light Energy It is the energy in each photon of light that causes a chemical change to the photographic detectors that are coated on the film. The process whereby electromagnetic energy causes chemical changes to matter is known as photochemistry

Film Crystals and Light Sensitivity Organic molecules known as spectral sensitizers are added to the surface of the grains to make them more sensitive to blue, green and red light. The imaging layers contain sub-micron sized grains of silver-halide crystals that act as the photon detectors These chemicals affect the light sensitivity of the grain, also known as its photographic speed (ISO or ASA rating).

Recording Light Color film has three different layers of light-sensitive materials, which respond, in turn, to red, green and blue. When the film is developed, these layers are exposed to chemicals that dye the layers of film. When you overlay the color information from all three layers, you get a full-color negative.

Film Speed ISO and ASA speed ratings are also generally printed somewhere on the box. The higher the number, the "faster" the film. "Faster" means increased light sensitivity. You want a faster film when you're photographing quickly moving objects and you want them to be in focus, or when you want to take a picture in dimly lit surroundings without the benefit of additional illumination (such as a flash).

Next, the proper exposure must be set. The first step after loading the film is to focus the image on the surface of film. Next, the proper exposure must be set. The next two factors are interdependent, since the exposure to the film is the product of light intensity and exposure time. The light intensity is determined by how much reflected light is reaching the film plane

There is an advantage to having a faster film in your camera There is an advantage to having a faster film in your camera. It allows you to have a smaller aperture setting for the same exposure time. This smaller aperture diameter produces a larger depth of field. Photographic film has a limited exposure latitude. If it is underexposed, it will not detect all the reflected light from a scene

Click By opening the camera's shutter for a fraction of a second, you formed a latent image of the visible energy reflected off the objects in your viewfinder. The brightest portion of your picture exposed the majority of the silver-halide grains in that particular part of the film. In other parts of the image, less light energy reached the film, and fewer grains were exposed. The image is called "latent" because you can't detect its presence until the film is processed