In our last post, we talked about exposure reciprocity and how there are many combinations of the aperture, shutter speed and ISO settings that can yield a properly exposed photo. And with that, we saw how this idea of equivalent exposures gives us creative flexibility when choosing a combination of these exposure controls.
In this post, we are going to talk about one of these controls, shutter speed. We’ll look at how it affects the look of your images, when the choice of shutter speed becomes particularly important and why you might choose one shutter speed over another.
What Is Shutter Speed?
When you press your camera’s shutter button, a small curtain inside of your camera opens and closes to allow light to strike the image sensor and create a photo. The amount of time that the curtain is open is the shutter speed.
When we talk about a shutter speed being fast, or short, we are saying that this curtain is only open for a short period of time.
On the other hand, a slow, or long, shutter speed means that the curtain is open for a relatively long time.
Given this, it makes sense that a longer shutter speed lets in more light than a shorter one.
How Does Shutter Speed Affect The Look Of A Photo?
Shutter speed impacts the look of an image in two ways.
Shutter Speed Controls Exposure
The amount of light that hits the image sensor increases as the shutter speed gets longer. So the shutter speed is directly related to exposure, affecting the brightness or darkness of an image.
Shutter Speed Determines How Motion Is Displayed
The shutter speed determines how motion appears in an image.
A fast shutter speed freezes motion so that the moving object appears to be standing still:
On the other hand, a slow shutter speed shows the movement in the scene, displaying it as motion blur in your image:
When The Choice Of Shutter Speed Really Matters
The choice of shutter speed becomes especially important when something in your scene is moving. And while motion can be a factor in any situation, it is often an issue when shooting sports and wildlife.
If there is movement in your scene, you have a choice.
You can use a combination of the exposure settings that includes a fast shutter speed so that you can freeze the motion in your scene.
Or, instead, you can decide on an exposure combination that has a slower shutter speed to show motion blur.
So this is where the idea of using equivalent exposures to be creative in your photography comes into play. You can choose from among the many combinations of aperture, shutter speed and ISO settings that properly expose your image to give you the look that you want.
A Few More Things…
Here are some things to keep in mind when working with shutter speed.
Shutter Speed is measured in seconds
Shutter speed is a unit of time and, so, is measured in fractional and whole seconds.
Beware of camera shake
A slower shutter speed not only shows the movement of you subject. It also shows any movement of the camera. So if you are shooting a low shutter speed–typically anything slower that 1/6oth of a second–you will probably need to mount your camera on a tripod or use some other support to avoid camera shake.
Quick movements can be hard to freeze
Depending on lighting conditions and the maximum aperture size of your lens, you can run into trouble getting a fast enough shutter speed to completely freeze the motion in your scene. If your subject is moving quickly, the shutter speed needed to completely free movement may not allow enough light to get to the camera sensor and you can end up with an underexposed photo.
If this is the case, don’t be afraid to increase the ISO a bit to give yourself more flexibility in terms of shutter speed. And adding light to the scene, by using a flash for example, will also help.