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12 APERTURE
Blurring part of the picture can heighten the sense of action. In most cases, how-
ever, image blur is undesirable. To avoid blurred pictures from camera movement,
choose a shutter speed of at least 1/60 sec. for handheld shooting with a standard
lens.
With a telephoto lens, it is advisable to use faster shutter speeds. The rule of thumb
is to use a shutter speed no slower than the reciprocal of the lens in use. This means
that for a 100mm lens, the shutter speed should be at least 1/125 sec.; for a 500mm
lens, it should be at least 1/500 sec.
12 Aperture
The size of the aperture determines the amount of light allowed to reach the film.
The apertures are indicated by a series of numbers, called f/stops or f-numbers,
iV‘hich can be found on the aperture ring. The smaller numbers are called large
f/stops while the larger numbers are called small f/stops. This is because the smaller
numbers represent larger apertures which allow more light to pass through the lens.
The largest f/stop on the lens is called the lens maximum aperture; the smallest
f/stop the lens minimum aperture. The maximum and minimum apertures differ
depending on the lens.
Each time you turn the aperture ring from one f/stop to the next smaller one,
the amount of light allowed through is exactly halved. Using f/2 as a standard, the
amount of light striking the film will change according to the f/stop indicated below.
How the Aperture Affects the Picture
In addition to controlling the quantity of light, the aperture influences depth of field
which, in turn, affects the way a picture will look. When your subject is in focus,
there is a certain area in front of and behind it which will also be in focus. This
range of sharpness is called depth of field.
f/stop (1.2) 1.4 (1.8) 2 2.8 4 5.6 8 11
Brightness ratio 3 2 1-1/4 1 1/2 1/4 1/8 1/16 1/32
f/stop 16 22 32
Brightness ratio 1/64 1/128 1/256
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