Photography is an art that relies heavily on light. In order to correctly capture the image before the viewer, a camera must successfully capture the correct amount of light. This capturing of light relies on film exposure.
By pressing the shutter button, one allows light to strike the film and take a picture and by setting the exposure, one can control how much light is allowed to enter the camera, therefore influencing the way a scene will be depicted. When too much light is let in, overexposure occurs, but when too little light reaches the film, underexposure results. In order to achieve the correct amount of exposure, one must understand many contributing factors such as subject lighting, lens aperture, shutter speed, and film speed.
Obviously, one must learn to compensate for the amount of light that surrounds a subject. When the subject is dimly lit, more light should be allowed within the camera yet when there’s an excess of light, it should be restrained. This control can be adjusted through the camera’s lens aperture through f-stops, the shutter speed through intervals, or even the film’s speed or sensitivity to light. When choosing an f-stop, one must determine whether a larger or smaller lens opening is required. The larger the f-stop number, the smaller the lens opening. The opposite is true of shutter speeds, however. The smaller the fraction, the shorter the amount of time the curtain within the camera is opened and the less light is allowed to reach the film. While lens aperture and shutter speed are the factors most often considered when dealing with film exposure, the film itself may also play a role as films with higher ISO numbers are more highly sensitive to light than films with lower ISO numbers. All factors must be considered in order to correctly set a camera’s exposure and accurately depict a scene.
By understanding each factor that determines the film’s exposure to light, one can more accurately capture the correct amount of light and more accurately create the scene that is desired. Because light is essential to creating successful negatives, it is important to understand and master the factors that govern it.