44 How to Do Everything: Digital Camera
to f/8 or f/11 to f/16, doubles or halves the available light, depending upon which way you??™re
going. If you adjust a lens from f/8 to f/11, for instance, you??™ve reduced the light by half.
We??™ll talk about this in more detail in Chapter 4 (it??™s really important, yet really simple), but
for the moment take a look at Figure 3-2. This diagram shows the relationship between the f/stop
and the shutter speed. If you reduce the shutter speed, you need to increase the diameter of the
aperture in order to have enough light to take a properly exposed picture.
This concept??”that there are many equivalent exposure possibilities by varying the shutter
speed and aperture??”is illustrated in Figure 3-3. Here??™s how it works: If you know that any given
combination adds up to a good exposure (let??™s say f/5.6 at 1/60 second), then you can find an
equivalent exposure setting by traveling along a diagonal line. In this example, f/4.0 at 1/125
second will yield the exact same exposure.
FIGURE 3-2 Each of these combinations results in the same amount of light reaching the film.
FIGURE 3-3 You can see how shutter speeds and aperture settings relate to each other in an
Exposure Equivalency chart.
1/30
f/2.
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