Shutter Speed
General
Shutter speed determines the length of time the shutter is open. It is the second half of the exposure equation, along with aperture. Shutter speed is set in relation to aperture, and controls the apparent motion of the subject. Like aperture, each shutter speed setting represents one stop, and is twice or half the duration of the setting preceding or following it.
The table below lists standard shutter speeds, with notes on some.
| 8 sec | Usually subject to reciprocity failure. |
| 4 sec | |
| 2 sec | |
| 1 sec | Reciprocity failure becomes issue |
| 1/2 sec | |
| 1/4 sec | |
| 1/8 sec | |
| 1/15 sec | |
| 1/30 sec | |
| 1/60 sec | Slowest to hand-hold camera; freezes walking |
| 1/125 sec | |
| 1/250 sec | freezes running |
| 1/500 sec | |
| 1/1000 sec | |
| 1/2000 sec |
In addition to the standard increments, there are some special settings for shutter speed:
B (bulb)
On Bulb, the shutter remains open as long as the shutter release is depressed. Usually used (with a cable release) for long exposures.
T (Time)
Like B, Time is used for long exposures. In the case of the Time setting, the shutter is opened by the shutter release, and remains open until the release is pressed again.
Flash Sync
The flash sync speed (usually 1/60, 1/125, occasionally 1/250) is indicated by an X, a lightning bolt, or by a different color. This is ths ONLY speed at which the camera is designed to use a flash or strobe. At this speed, the shutter will open completely, the strobe will fire, and then the shutter will close. At any slower speed, the strobe will fire before the shutter is completely open, at a faster speed, the shutter will be closing (or closed) as the strobe is firing. Both situations will result in partially correct expsures.
Automatic Settings
Since they are usually located on the shutter speed dial, there are a few other letters that should be explained. These are not on all cameras, but represent automatic setting options.
A or P
Automatic or Program. Usually this means fully automatic: the camera will select a combination of shutter speed and aperture for you. You just press the button.
Ap, Pa
There are various combinations of indications, but this setting is aperture-priority automatic. In this case, you set the aperture, and the camera selects the proper shutter speed. (since the aperture setting contols depth of field, this is usually the preferred auto mode).
As, Ps
These (and various other) settings represent shutter-priority auto, where you set the shutter speed and the camera sets the aperture. Probably best used when attempting to freeze motion with sports or similar situations.
