In this tutorial, we will take a close look at one aspect of the exposure triangle – shutter speed. In my previous tutorial on Understanding Exposure in 7 Steps, I explained that the process of exposure requires three components, ISO, Shutter speed, and aperture. Each of these three components work together to record light.
The exposure process is the technical process of recording a “moment” of light. The total amount of light that is being recorded is dependent on the three aspects of the exposure triangle. Shutter speed dictates the total amount of time that light is allowed to expose the “recording device” (film, digital imaging sensor).
Each component of the exposure triangle, has both an effect on the exposure process and also an effect on the creative aspects of the photograph. ISO introduces noise in an image; aperture controls the depth of field; and shutter speed allows us to introduce blur.
Step 1: Shutter Speed and Exposure
Out of the three components of the exposure triangle, shutter speed is perhaps the easiest to understand. Shutter speed allows us to control the length of time that light is being recorded onto the film or digital imaging sensor (recording device).
On most digital SLR cameras, there are two “shutter curtains” which prevent light from hitting the film or digital imaging sensor. When you “take a photo” you are pressing the shutter release button. This opens the curtains for a specified period of time and allows light to “expose” the recording device. For a spectacular frame-by-frame photo sequence of the shutter curtains in action, head over here.
Vertical Focal Plane Shutter: Two shutter curtains (closed) prevent light from “exposing” the “recording device” (film, digital sensor) until the shutter release button is pressed.
Shutter Curtains in Action: Shutter curtains open at 1/500th second. Note how the rear curtain closes before the front curtain is fully open, creating a “shutter gap.”
- SLOW shutter speeds allow MORE light to be exposed on the recording device.
- FAST shutter speeds allow LESS light to be exposed on the recording device.
How is shutter speed represented?
Shutter speed is represented in units of time. On your camera, it is specifically represented in seconds. The numbers displayed indicate fractions of a second. So you will see 500 on your camera display, which will indicate a shutter speed of 1/500 of a second.
Each doubling of time, corresponds to a doubling of the exposure. So a shutter speed of 1/125 gives double the exposure of 1/250. 1/125 is twice 1/250 because the slower shutter speed allows two times more light to be exposed.
Bulb mode. Most cameras have a “bulb” mode setting. Bulb mode allows you to keep the shutter open for as long as the shutter button is pressed down. This gives you more creative control over your shutter speed.
Time mode. Additionally, some cameras offer a “time” mode setting for shutter speed. Time mode will keep the shutter open until the shutter button is pressed again. You press once to open the shutter and press again to close it.
Step 2: Shutter Speed Characteristics: Motion Freeze and Motion Blur
Remember, each component of the exposure triangle has two effects. The first effect is controlling how much light is being recorded. The second effect is introducing a creative aspect into the photograph. The creative effect that shutter speed has on a photograph is it’s effect on motion.
- Slow shutter speeds introduce motion blur.
- Faster shutter speeds freeze motion (motion freeze).
There are two types of motion that can be captured in a photograph. Motion as a result from movement of the camera (camera-induced motion), or motion as a result of the subject itself moving (subject-induced motion).
Camera-induced motion is when the camera moves during an exposure. This is also referred to as “camera shake.” This creates blur in the entire scene of the photograph.
Focal length. Focal length amplifies camera-induced motion. The longer the focal length you use, the greater the degree of camera shake you will see.
1/60 guideline. If you are hand-holding your camera, the general guideline is not to shoot slower than 1/60. Your results may vary and depend entirely on your technique.
Camera-Induced Motion Blur: Hand holding a camera in low-light conditions with a slow shutter are ideal conditions for camera shake. Photo courtesy of Dean Ayres
Subject-induced motion is when the subject moves during an exposure. Any object that is moving during the exposure will come out blurred in the photograph. This can range from the entire subject moving, or just a part of the subject, e.g. arm or leg.
Hummingbird in Flight: A fast shutter speed is needed to “freeze” the flight of a hummingbird whose wings flap upwards of 80 times a second. Photo courtesy of nebarnix
Step 3: Shutter Speed Application
Now that you know what shutter speed is and it’s properties, let’s see how we can apply this knowledge.
How much available light do I have?
The first issue you want to address is exposure. Without proper exposure, you will not have a viewable photograph.
Ask yourself, “do I have enough light?” If you find yourself in a situation without sufficient light, then you can use a slow shutter speed to get a good exposure. Conversely, in well-lit scenes, choosing a fast shutter speed prevents your photograph from being over-exposed. The shutter speed you use will be dependent on the ISO and aperture settings as well.
Star Trails: Night shots require long shutter speeds. A series of 30 second exposures were composite together to form this image. Photo courtesy of Andrew Stawarz
Do I want motion blur in photo?
Motion blur can be used as an artistic technique. Whether or not you want blur in your image is a matter of taste and desired effect. Motion blur may be beneficial if you are trying to portray speed, movement, or confusion.
If you want to introduce motion blur, use a slow shutter speed that will allow you to capture the movement of the subject. The shutter speed you choose will be dependent on the degree of the motion effect you desire and the movement of the subject.
If you don’t want motion blur in your photo, then you will need to use a faster shutter speed that will help you to “freeze” the motion. Again, the shutter speed you set will be dependent on how fast the subject is moving and the degree of the motion freeze you desire.
Bboy Airflares: A shutter speed of 1/60 was used to capture the motion blur from the subject.
Shutter Speed Practice
Shutter speed is an important element in photography. It is a fundamental skill that must be mastered and practiced daily.
Go out and take photos with different shutter speeds to see how it has an effect on your exposure. Take some photos of moving objects at different shutter speeds to see how it can freeze motion and blur motion.