- Compose
and focus the image.
- Stop down or open
up the diaphragm until the desired depth of field is
achieved.
- Select the shutter speed that will produce a proper
exposure when combined with your aperture setting.
- Determine whether the shutter speed is fast enough
to prevent image blurring.
- If the selected shutter speed is too slow, reset
it to a faster speed and open up the aperture accordingly
W
hen you increase the shutter speed, you compromise
and loose depth of field. Sometimes this is the only way to
produce a useable image. If you cannot sacrifice some depth
of field, there are several alternative you can use: select
a higher ISO, increase the camera-to-subject distance, select
a shorter focal length lens, or change the camera angle, so
the relative motion of the subject to the camera is decreased.
There are five factors that determine the distance an image
moves on the film during exposure. You must consider these
factors each time you photograph a moving object. These five
factors are as follows:
- The lens-to-subject distance
- The lens focal length
- The speed of the object perpendicular to the lens axis
- The direction of movement
- The exposure time
Whenever one of these five factors change, the distance
the image moves during exposure also changes.
The first four factors determine the speed that the image
moves across the sensor. The fifth factor limits the time
it is allowed to move, thereby limiting the distance of image
movement.
Subject movement on the sensor plane is greatest when the
subject is moving across the angle of view of the lens (perpendicular
to the lens axis). For example, when the subject is moving
straight towards or straight away from the camera, it may
appear as though it is hardly moving and a fast shutter speed
is not required to produce a sharp image; however, when that
same subject moves at the same speed across the field of
view of the camera, the speed of the subject appears much
faster. A faster shutter speed is required to stop the action
in this case.
The camera-to-subject distance also affects the amount of
image movement at the film plane; for example, a car moving
across your field of view at 55 mph from a distance of 700
yards appears to be moving slowly. The same car moving at
55 mph and only 15 feet away appears to be moving very fast;
therefore, the closer a moving object is to the camera, the
faster the shutter speed must be to capture a sharp image.
When the subject is moving diagonally across your angle of
view, movement is more apparent than when moving straight
away or toward the camera, but less apparent than when moving
straight across the field of view.
Remember, long-focal-length lenses exaggerate the effects
of camera and subject movement, and short-focal- length lenses
reduce the effect.
Experience and common sense are your best guides for determining
shutter speed that will minimize image movement, but the
following can be used as a guide to help make these determinations:
- Double the shutter speed when the subject speed is doubled.
- Halve the speed when the speed of the subject is halved.
- Double the shutter speed when the camera-to-subject
distance is halved.
- Halve the shutter speed when the camera-to-subject distance
is doubled.
- Double the shutter speed when the focal length is doubled.
- Halve the shutter speed when the focal length is halved.
- When in doubt, use the next higher shutter speed.
There are mathematical formulas used to determine appropriate
shutter speeds for subjects moving at all speeds when photographed
with various lenses, but the use of these formulas is not
practical.
The table below shows some suggested shutter speeds designed
to "freeze" subject movement.
Speed
MPH |
Type
of Action |
Distance |
Direction
of Action |
Perpendicular |
Diagonal |
Inline |
0 |
Landscape
or still scene with no movement |
|
1/30
|
1/30
|
1/30
|
5 |
Slow walk, working with
the hands |
|
|
|
|
10 |
Fast walk/ work, slow-moving
vehicles |
|
|
|
|
25 |
Running sports, very
active people, vehicles moving at a moderate speed |
|
- 1/2000
- 1/1000 1/500
- 1/250
|
|
|
100 |
Very
fast-moving vehicles, aircraft, animals and birds |
|
|
- 1/2000
- 1/1000 1/500
- 1/250
|
|
"Action Stopping" Shutter
Speeds for Normal-Focal-Length Lenses
Original article is located at at this URL.
