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t o help you select an appropriate shutter
speed when using a standard 50mm lens. For
indoor photography, with no special illumi-
nation, choose 1/30 of a second and 1/60 of
a second in a brightly lit room.
For outdoor photography, select 11125
second when cloudy and 11250 second in
sunshine. To take pictures in particularly
bright sunshine such as at a beach in mid-
summer or in snow-covered mountains, use
shutter speeds of 11500 sec. or 1 11 000 sec.
The above mentioned shutter speeds
apply when using a standard 50mm lens, but
it i s necessary to choose faster shutter speeds
when using lenses of longer focal lengths
because they are more difficult to hold
steady. It is generally said that the shutter
speed figure should be greater .than 1 divided
by the focal length of the lens in order t o ob-
tain sharp images.
For example, when using s 200mm tele-
photo lens, shutter speed should be faster
than 11200 second. Therefore, the .shutter
speed in this particular case shiould be set a t
11250 sec. Image blur can also arise if the
camera i s not properly held. See page 37.
Lens Aperture
The adjustment of the aperture i s used
with the shutter speed t o get the correct ex-
posure. The amount of light reaching the film
i s controlled by the aperture's size.
On the aperture ring are a series of mark-
ings which indicate the proportion of the light
allowed to pass through the lens, which are
known as flnumbers. When the aperture ring
i s set to the next larger flnumber on the scale
of the ring, the amount of light passing
through the lens is decreased by 112. The
lens's brightness i s based on the smallest
numerical aperture value for the lens.
With a f/2 serving a s the standard, the com-
parative brightness at each flstop will be as
indicated below.
R a t i o
1
3
2 u 1 / 2 1 / 4 118 1 / 1 6 1/22 1/64
Brightness
(flstop)
The aperture ring can be set at positions
between the settings on the scale.
1.2 1.4
fi
2.8
4
5.6
8
11
1 6
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