Introduction to Shutter Speed in Digital Photography
Previously I’ve introduced the concept of the Exposure
Triangle as a way of thinking about getting out of Auto Mode and
exploring the idea of manually adjusting the exposure of your shots.
The three main areas that you can adjust are ISO, Aperture and Shutter
looked at making adjustments to ISO and now want to turn our
attention to shutter speed.
What is Shutter Speed?
As I’ve written elsewhere, defined most basically – 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
- 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.
Shutter Speed – Bringing it Together
Remember that thinking about Shutter Speed in isolation from the
other two elements of the Exposure Triangle (aperture and ISO) is not
really a good idea. As you change shutter speed you’ll need to change
one or both of the other elements to compensate for it.
For example if you speed up your shutter speed one stop (for example
from 1/125th to 1/250th) you’re effectively letting half as much light
into your camera. To compensate for this you’ll probably need to
increase your aperture one stop (for example from f16 to f11). The
other alternative would be to choose a faster ISO rating (you might
want to move from ISO 100 to ISO 400 for example).
I’ll write more on bringing it together once I’ve written a post in
the coming week on the last element of the Exposure Triangle – Aperture.
Update: Want more control of your Digital Camera?
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and Bolts: Know Your Camera and Take Better Photos.