Controls for Creating Effective Images on
Film or Digitally
The image in the camera, whether produced on a digital sensor or on fi lm, is created by the
lens and its effectiveness is determined by the focal length of the lens, the distance setting,
and the settings of the aperture and shutter speed controls. The last two also determine the
exposure, but we must be aware that the same exposure can be obtained with many different
combinations of aperture and shutter speeds. These controls therefore must be determined
not only for producing correct exposure but also for creating visually effective images.
APERTURE CONTROL
Lenses are distinguished by their maximum aperture, usually engraved on the lens, and are
often referred to as the “speed” of the lens. Large aperture lenses are frequently known as
“fast” lenses. The aperture number is determined by the size of the diaphragm opening which
can be set to different numbers with a low number, such as f/2.8, indicating a larger opening
than f/5.6. The amount of light reaching the image plane is reduced by setting the aperture to
a higher number, such as f/11. A change in aperture from one setting to the next either dou-
bles or halves the amount of light reaching the image plane.
Because aperture and shutter speed together determine the total amount of light that
reaches the image plane, you must change the shutter speed when changing the aperture.
Because aperture numbers double or halve the amount of light, it is easy to adjust the shutter
speed to compensate for a change in aperture. Change it from
1
/
60
to
1
/
125
when you open the
aperture one f stop and do the opposite when changing from
1
/
60
to
1
/
30
.
Distance Setting and Exposure
On many modern lenses, focusing is accomplished optically by moving some of the lens com-
ponents (internal focusing) or rear or front focusing on the H camera lenses depending on
whether the focusing is accomplished with the rear or front elements. One is not better than
the other, just different in design. Such lenses can be used at any distance without the need
for adjusting exposure.
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