The Basics: Shutter Speed
To put it simply, Shutter Speed is the length of time the digital sensor, or film, is exposed to light while the shutter is open. I gave you a brief introduction to Shutter Speed in Shooting Modes when I mentioned Shutter Priority Mode (Tv or S). You now also have a good understanding of Aperture and using Aperture Priority mode to allow the camera assist you in your creative shooting. In that mode, you choose the aperture and the camera figures out the Shutter Speed for you. But what exactly is the Shutter Speed all about and when would you want to manually control that? That’s what this post is all about and hopefully you will walk away with a good understanding of Shutter Speed so that you can start Going Beyond Auto!
Shutter speed is measured in seconds or a fraction of a second depending on how fast your shutter speed is. As with aperture, shutter speed doubles the amount of light passing through the sensor with each stop. You will see shutter speeds as 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, etc. Cameras are also capable of long exposures at 1s, 2s, 4s, 8s, 15s and 30s. Those are the full stops and your camera may include third-stops as well.
Your camera may also go beyond 30 seconds with a setting called “Bulb.” This allows you to take a single exposure for a minute or a couple of hours depending on your needs. Old cameras had an actual bulb (like you would pump a blood-pressure cuff with) on a tube attached to the camera’s shutter release. As long as you squeezed the bulb, that’s how long of an exposure you would get. You have the same Bulb feature on most modern cameras, but now you are holding down a digital shutter release button with your finger, either on the camera, or using a connected remote to reduce camera shake. Advanced shooters will use an intervalometer that allows them to specify exactly how long they would like the shutter exposed in bulb mode.
Motion (Stopping or Showing)
Our cameras allow us to open up a world of creativity, and the shutter speed is one of the main doors into that world with the ability to control motion in your photos. Two or more pictures of the same subject taken at different shutter speeds can dramatically change the overall look and feel of the end result of your picture. However, you can only have these creative changes if you get your camera out of Automatic mode.
When your camera is set to auto, the light sensors and fancy electronics inside are going to attempt to take a picture with the fastest shutter speed, and widest open aperture possible. If it doesn’t think there is enough light, instead of slowing the shutter speed down too much, it will fire your flash so your picture doesn’t get blurry. Most cameras are designed to take general portraits with the camera handheld, and they will automatically try to expose the shot with that in mind. That works out great a lot of the time when you are taking pictures at birthday parties, group events or pictures around the house. However, that doesn’t allow for much in the creativity department. What if you want to show that your child is running, the river is flowing, or the fireworks are exploding? What if you want to show a single drop of water hitting a pond, or stop a hummingbird’s wings? All that is controlled by your Shutter Speed and cannot be done in Auto mode.
To show motion in your images, you need a slow Shutter Speed. This means that the image is being exposed for a longer period of time, therefore you are capturing more time in one exposure. A typical camera during typical lighting conditions may try to capture an image at 1/125th of a second or faster. That’s great, but if you want to show water flowing over rocks in a river you will need to take a much longer exposure. The key to taking longer exposures is a good solid tripod because you will also pick up any movement the camera makes as well which could ruin your picture. The other key is the amount of light, obviously the longer your shutter is open, the more light gets to the sensor, and the brighter the final image will be. In some instances, there may be too much ambient light to slow down the shutter as much as you would like to. In that case you may need to put a Neutral Density, or ND, filter on the front of your lens. ND filters block light by 1 or more f-stops without changing the color of the scene. Filters are another post for another day, but I want you to be aware that you may not be able to achieve the shot you are looking for without one if it is too bright in your scene.
The Shutter Speed you choose for your particular image is really a personal preference. In general, if you want to start showing motion you will use a shutter speed slower than 1/60. I say in general, because your focal length plays a role in which shutter speed you should use, more on that in a minute. Keep in mind, you will most likely want to use a tripod to avoid what is known as Camera Shake. Camera Shake is any movement of the camera during an exposure that will make your image blurry. The slower your Shutter Speed, the more motion that will be captured, as long as the lighting is right.
Below is an example of a river running over rocks. The image on the left has not quite stopped motion, but it doesn’t exactly show the river flowing either. The image on the right however shows the flow of the water. You have probably seen images of incredibly soft, dream like water…that is done with a very slow shutter speed. In this particular scene, I could not slow down the water any more due to the amount of sunlight without using an ND filter. I also did not want the wheel on the mill to be too blurry. The best times to capture rivers and waterfalls is in the morning or evening when the sunlight is not as much of a factor.
To stop motion in your images you are going to need a fast Shutter Speed. Generally a shutter speed of 1/125 or faster will stop motion depending on what you are trying to stop, the amount of light, your focal length, and the distance and direction of the movement…a lot to think about. The first thing to consider is personal taste, and that is how much of the motion you would like to stop…totally up to you. The amount of light may or not be something you can control. Typically brighter scenes allow for faster shutter speeds and more motion that can be stopped. You can always add constant lights or a flash if you need more lighting in your scene. We will talk about focal length in another section, so hang tight on that one.
The distance and direction of your subject on the other hand plays a big part in how you stop the motion. Even if the object is moving at the same speed, the closer you are to the object, or the object is to you, the faster it will appear to be moving therefore the faster the shutter speed will need to be. Obviously the further way the object, the slower it will appear to be moving and you can use a slower shutter speed to stop the motion. The direction of the movement also plays a huge role in determining the shutter speed to stop motion. Objects moving toward or away from the camera will require a slower shutter speed than objects moving side-to-side in your shot. For instance if somebody is moving toward you, you could probably stop their motion at about 1/500. However, if they are moving from one side of your frame to the other, you may need 1/800 or faster depending on how fast they are moving as the motion is more pronounced at this angle.
In the images below, I have captured a humming bird eating out of a feeder in my backyard. The image on the left would be an acceptable picture of a humming bird in flight, with the rapid wings in motion. However, the image on the right allows you to stop the wings motion and see the detail and color. In order to use such a fast shutter speed, I had to be sure there was enough daylight available to light the bird.
Shutter Priority Mode
Just like Aperture Priority mode, Shutter Priority is a semi-automatic mode that helps you step away from auto without being scared away by manual. This mode allows you to control your shutter speed, and the camera will figure out a matching aperture to properly expose your image. This mode is best for creative control when you want to stop or show motion and you don’t necessarily care about depth of field. I recommend this mode when you are chasing after your kids trying to take their picture and you know you need a fast shutter speed, or when you are trying to show that beautiful waterfall motion and you need to slow it down.
Shutter Speed and Focal Length
The focal length at which you take your picture will help you determine your shutter speed depending on the type of motion you want. As I mentioned before, when you are trying to show motion, you will need a good steady tripod to avoid moving the camera and blurring your picture. This changes however depending on the focal length you are shooting at. A good rule of thumb is to use a shutter speed faster than the focal length. This means if you are shooting with your lens at 200mm, you will want to use a shutter speed of at least 1/250s or faster to compensate for the movement of your camera. If you are using a 35mm lens however, you only need a minimum of 1/60s to avoid camera shake. This means the longer your lens, the faster your shutter speed will need to be or you will need a tripod.
Cropped Sensors and Focal Length
Most consumer digital cameras have what is referred to as a Cropped Sensor. Back in the days of film, one frame of 35mm film was 24mm x 36mm and that was the basis for determining everything on your camera. If you shot with a 200m lens on a film camera, your photograph would be at 200m. If you have paid a good amount of money for a full-frame camera, that means that your sensor size is roughly 24mm x 36mm and is the equivalent of a 35mm film camera and your image would look the same on either one. However, as I mentioned, most consumer DSLR cameras have a sensor that is smaller to make the camera more affordable. Most consumer Canon DSLR cameras have what is called a crop factor of 1.6x. The size of your sensor is roughly 60% of a full-frame sensor.
If you only have the lens that came with your camera you are in good shape as this lens was designed for your cropped sensor. When you shoot a picture at 50mm, it will be 50mm. However, if you buy a nicer lens like the Canon 24-70mm (sponsored link), that lens was designed for a full-frame camera. This lens is designed to expose on a bigger sensor than your camera has, so you will essentially lose the outside edges of your image. This gives the illusion of greater focal length than the lens says according your your crop factor. If you shot at the same 50mm with this new lens, your resulting image is the equivalent of an 80mm lens. To determine that number, take the focal length 50mm and multiply it by your camera’s crop factor 1.6 to get 80mm.
Why should you care about what size your sensor is? If you bought a Canon 70-200mm (sponsored link) lens to take pictures and you have a cropped sensor, that 200mm is really more like 320mm and you will need a shutter speed of at least 1/500s to avoid camera shake and blurry pictures.