I found an excellent article that explains shutter speeds for the aspiring photographer! Enjoy!
What is Shutter Speed?
Shutter speed is ‘the amount of time that the shutter is open’.
In film photography it was the length of time that the film was
exposed to the scene you’re photographing and similarly in digital
photography shutter speed is the length of time that your image sensor
‘sees’ the scene you’re attempting to capture.
Let me attempt to break down the topic of “Shutter Speed” into some
bite sized pieces that should help digital camera owners trying to get
their head around shutter speed:Shutter speed is measured in seconds – or in most cases fractions of seconds. The bigger the denominator the faster the speed (ie 1/1000 is much faster than 1/30).
In most cases you’ll probably be using shutter speeds of 1/60th of a second or faster.
This is because anything slower than this is very difficult to use
without getting camera shake. Camera shake is when your camera is moving
while the shutter is open and results in blur in your photos.
If you’re using a slow shutter speed (anything slower than 1/60) you will need to either use a tripod or some some type of image stabilization (more and more cameras are coming with this built in).
Shutter speeds available to you on your camera will usually double (approximately) with each setting.
As a result you’ll usually have the options for the following shutter
speeds – 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8 etc. This ‘doubling’
is handy to keep in mind as aperture settings also double the amount of
light that is let in – as a result increasing shutter speed by one stop
and decreasing aperture by one stop should give you similar exposure
levels (but we’ll talk more about this in a future post).
Some cameras also give you the option for very slow shutter speeds
that are not fractions of seconds but are measured in seconds (for
example 1 second, 10 seconds, 30 seconds etc). These are used in very
low light situations, when you’re going after special effects and/or
when you’re trying to capture a lot of movement in a shot). Some cameras
also give you the option to shoot in ‘B’ (or ‘Bulb’) mode. Bulb mode
lets you keep the shutter open for as long as you hold it down.
When considering what shutter speed to use in an image you should always ask yourself whether anything in your scene is moving
and how you’d like to capture that movement. If there is movement in
your scene you have the choice of either freezing the movement (so it
looks still) or letting the moving object intentionally blur (giving it a
sense of movement).
To freeze movement in an image (like in the surfing
shot above) you’ll want to choose a faster shutter speed and to let the
movement blur you’ll want to choose a slower shutter speed. The actual
speeds you should choose will vary depending upon the speed of the
subject in your shot and how much you want it to be blurred.Motion is not always bad – I spoke to one digital
camera owner last week who told me that he always used fast shutter
speeds and couldn’t understand why anyone would want motion in their
images. There are times when motion is good. For example when you’re
taking a photo of a waterfall and want to show how fast the water is
flowing, or when you’re taking a shot of a racing car and want to give
it a feeling of speed, or when you’re taking a shot of a star scape and
want to show how the stars move over a longer period of time etc. In all
of these instances choosing a longer shutter speed will be the way to
go. However in all of these cases you need to use a tripod or you’ll run
the risk of ruining the shots by adding camera movement (a different
type of blur than motion blur).Focal Length and Shutter Speed - another thing to
consider when choosing shutter speed is the focal length of the lens
you’re using. Longer focal lengths will accentuate the amount of camera
shake you have and so you’ll need to choose a faster shutter speed
(unless you have image stabilization in your lens or camera). The ‘rule’
of thumb to use with focal length in non image stabilized situations)
is to choose a shutter speed with a denominator that is larger than the
focal length of the lens. For example if you have a lens that is 50mm
1/60th is probably ok but if you have a 200mm lens you’ll probably want
to shoot at around 1/250.