Previously, I introduced the concept of the exposure triangle as a way of thinking about getting off of Auto Mode and exploring the idea of manually adjusting the exposure of your shots.
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, shutter speed is the length of time that the film is exposed to the scene you’re photographing. 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 (i.e., 1/1000s is much faster than 1/30s).
- In most cases, you’ll probably need 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; it causes blur in your photos.
- If you’re using a slow shutter speed (anything slower than 1/60s), you will need to either use a tripod or some type of image stabilization technology (more and more cameras are coming with this built-in).
- Shutter speeds available on your camera will often double (approximately) with each setting. As a result, you’ll generally have the option to use the following shutter speeds: 1/500s, 1/250s, 1/125s, 1/60s, 1/30s, 1/15s, 1/8s, 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 the shutter speed by one stop and decreasing the aperture by one stop should give you similar exposure levels.
- 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 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 the shutter button 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 shots of the bird above and the surfer below), you’ll want to choose a faster shutter speed. 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.
In the bird image above, the shutter speed was 1/1000th of a second, meaning that despite the bird’s fast-flapping wings, they appear to be frozen in a split second of time. The surfing shot below had a fast shutter speed (around 1/4000th of a second), which captured even the splashing drops of water sharply.
- 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. But there are times when motion is good. For example, when you’re taking a photo of a waterfall or a seascape 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 starscape and want to show how the stars move over a longer period of time. In all of these instances, choosing a longer shutter speed will be the way to go. However, in all of these cases, you will need to use a tripod or you’ll run the risk of ruining the shots by adding camera movement (which results in a different type of blur than motion blur).
For example, in the following waterfall photo, the shutter speed was around 1s, so we see the movement in the water:
In the subway shot below, the shutter speed was around 2s, so the movement of the train is beautifully blurred:
- Focal length and shutter speed – Another thing to consider when choosing your 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 here (in situations without image stabilization) 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, a shutter speed of 1/60s is probably okay. But if you have a 200mm lens, you’ll probably want to shoot at around 1/250s or higher.
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 your shutter speed, you’ll need to change one or both of the other elements to compensate for it.
For example, if you increase your shutter speed by one stop (for example, from 1/125s to 1/250s), you’re effectively letting half as much light into your camera. To compensate for this, you’ll probably need to increase your aperture by one stop (for example, from f/16 to f/11). The other alternative would be to choose a higher ISO (you might want to move from ISO 100 to ISO 200, for example).
I hope you’ve found this introduction to shutter speed useful. I would highly recommend you also put a little time aside today to learn about the other two important elements of the exposure triangle – aperture and ISO.
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