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
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 | 1/2 | 1/4 | 1/8 | 1/16 | 1/32 | |
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f/stop | 16 | 22 | 32 |
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Brightness ratio | 1/64 | 1/128 | 1/256 |
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