The numbers and markings on a camera's exposure system frightens more people than anything else. Actually, you need only two basic controls for proper exposure, apertures (diaphragm) and shutter speed.

The aperture controls that series of numbers 16, 11, 8, 5.6, etc. called F STOPS. Whenever we refer to a number preceded by f/ it means we are talking about aperture, the size of the opening in your lens through which light will pass during the exposure. When you change the f/stop, a diaphragm in the lens opens and closes, letting in more or less light. So, the f/stop controls the rate at which light enters the camera.

SHUTTER

The second exposure control is the shutter speed. Open the back of your camera and look inside toward the lens. Advance the shutter, point the camera to a bright or reflective object (not the sun), and watching the lens from the back of the camera, fire the shutter. What you see is exactly what the film sees. Change the speed and watch again. The shutter opens and closes at different rates of speed, depending on what speed you have selected.

The series of numbers on the shutter control refer to fractions of a second. "500" means 1/500 of a second. "2" means 1/2 of a second. The larger the number, the faster the lens is opening and closing - a 500th of a second is quite fast, while 1/2 of a second is very slow. .

The light that strikes the photosensitive film is cumulative - the longer the shutter is open, the more light that registers or "builds up'" on the film. So, from an exposure standpoint, the shutter speed controls the length or flow of time you allow the light from your subject to record on film. The shutter speed selection also is important in recording action - the faster the speed the more action stopping power.

APERTURE

Still looking through the back of your camera and pointing it at a bright source (not the sun) turn the aperture (f/stop) control. Notice how the lens opening gets larger or smaller depending on which way you turn the control. Each f/ number corresponds to a specific sized opening that delivers light at a consistent rate to the film, i.e., all lenses at f/8 deliver the same amount of light to the film.

The "F" system also represents fractions. Shutter speed, you recall represents fractions of a second of time. The aperture scale progression f/16, f/11 f/8, f/5.6, etc., means that the opening in the camera lens is that fraction of the focal length of the camera lens. The Yashica TLR for example, has an 80mm (3 ") focal length, this is imprinted right around the lens. So:

f/l6 means an opening of 1/16th x 3" = 3/16"

f/8 means an opening of 1/8th x 3" == 3/8"

f/4 means an opening of 1/4th x3" == 3/4"

From this it can be readily seen that the smaller the numerical number, the larger diameter the opening in the lens for light to pass through - f/4 (3/4" opening) lets in more light than f/8 (3/8" opening).

SPEED PLUS APERTURE EQUALS EXPOSURE

So those are the two camera exposure controls. Shutter speed controls the length of time light enters and the f/ stops control the rate at which light passes through the lens. It is the combination of both speed and aperture working together that gives proper exposure and allows you a creative license.

Each lighting condition (type of light, time of day, etc.) has it’s own exposure requirements as to the total amount of light needed to expose the film properly. What we need to realize is that you can control how you let the film receive the total light. You could let a little quantity (f/stop) of light record for a long time (shutter) or, you could let a large quantity record for a short time.

The following is a set of equivalent light exposure combinations. Note that as the shutter speed slows down, the aperture size gets smaller (remember smaller opening, larger numerical number).

1/500 - f/4

1/250 - f/5.6

1/125 - f/8

1/60 - f/11

1/30 - f/16

1/15 - f/22

Each shutter speed is either twice as fast or 1/2 as fast as the preceding one. In other words, if the camera were set to 1/125 of a second and you changed it to 1/250 it would be twice as fast. If you went to 1/60 of a second, it would be 1/2 the speed, allowing light to record twice as long on the film.

Likewise, each f/stop up and down the scale represents an opening that is 1/2 or twice as much light as the adjoining f/stop; i.e., f/8 is 1/2 the light as f/5.6 and f/4 is twice as much as f/5.6. So if you know what combination setting should be used for a given lighting condition - such as 125 at f/8 listed in the series above, then all the other combinations could be easily figured.