Shutter speed, aperture and lenses are three major controls in a film camera.
The shutter, aperture and lens are three different parts of a film camera. Shutter speed and aperture rely upon each other to bring in just the right amount of light to properly expose a given scene. The light passes through a lens, where it is focused before it reaches the film plane.
Shutter Speed
The shutter controls the amount of time light passes through to the film plane. The shutter is made from a series of thin interlocking metal sheets. Shutter speeds are listed as whole numbers, such as 125, though this number actually represents the shutter speed of 1/125 of a second. The numbers usually seen on a shutter speed dial include 1 (1 second), 2 (1/2 second), 4, 8, 15, 30, 60, 125, 250, 500, 1000, 2000. A long shutter speed creates blur where there is motion, and a short shutter speed freezes motion.
Aperture
Aperture controls the amount of light passing into the camera by a diaphragm, usually located within the lens. Aperture numbers are referred to as f-stops. On a 35mm camera, f-stops will generally include f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22 and f/32. The larger the number, the less light that passes through the camera. Smaller numbers create a shallow depth of field, meaning the amount of sharpness in the image beyond what is focused on is reduced. Larger numbers assure that more of the image, from foreground to background, will be sharp.
Lens
The lens on a film camera contains convex glass that focuses the image. Lenses are described by their focal length, or their distance from the node of the lens to the film plane when focused at infinity. Lenses are described as long, normal, or short (also called wide-angle). For a 35 mm camera, a long lens measures 58 mm or higher, which magnifies what the viewer sees and creates a narrower angle of view. A normal lens is typically 50 mm and approximates what the eye sees. A short lens is 4mm or less, creating a wider angle of view.
Shutter Speed and Aperture Together
A light meter in the camera determines what the proper shutter speed and aperture combination should be for a given scene. However, there is not just one setting that you must use to make an image. Shutter speed and aperture work inversely with each other; when light is decreased with an aperture change, the light must be increased with the shutter speed to compensate. In an average lighting situation, when a small aperture is used (large f-stop number), a long shutter speed time must be used and vice versa.
Lenses and Aperture Together
Long lenses generally create a more of a shallow depth of field. A lens of 85 mm may only be able to open up to f/4 at its widest. Also, depth of field of an 85 mm lens at f/4 will be much more shallow than a 28 mm lens at f/4. Wide angle lenses open up to wider apertures, some as much as f/1. They are often referred to as "fast" lenses because the wide apertures allow for faster shutter speeds. Wide lenses tend to generate a wider depth of field.
Tags: depth field, speed aperture, film camera, film plane, passes through, shutter speed, shutter speed