Shutter Speed (AKA – Exposure Time)
What is shutter speed and how does it affect our photos? In this tutorial I’ll explain:
Naturally, as our eyes are seeing constantly moving images, our retina is permanently exposed to the light.
However, this is not the case with photography. In order to capture an image you must expose the sensor or film to the light for a period of time, known as exposure time.
Inside your camera there is a shutter that acts as a kind of curtain. When the shutter button is pressed the curtain is pulled back and light is allowed to fall upon the sensor/film. The shutter is then closed and the image is frozen in place.
In essence, for the duration that the sensor/film is exposed the image is drawn upon it. With film the roll is moved on to another empty frame, and with digital the image is then transferred to the memory card and saved.
Shutter speed (exposure time) is measured in the time that the shutter is open, usually in a fraction of a second such as:
1/125 second (125th of a second).
Shutter speed adjustment is measured in stops:
- Full increments (double or half the previous speed)
- Half (1/2 a stop)
- Third (1/3 of a stop)
So for a shutter of 1/125, Shutter
- One stop slower is 1/60
- One stop faster is 1/250
The following table shows this.
Shutter speeds are a classic example of how the light draws the picture. Therefore, how long you expose for can make a huge difference to how your image looks. Any moving objects will be drawn according to the length of exposure.
Think about when you open and close your eyes. The longer your eyes are open, the more movement you see. If you open and close them quickly, you see less movement and retain more of a snapshot of the scene you looked at.
Imagine if you could open and close your eyes at 1/1000 second while watching someone jumping in the air in front of you. You would freeze them in mid air in your mind. Open your eyes for 1 second, and you would see the movement. If you keep your eyes fixed on one place, rather than track the jumper, then the action would be retained in your mind as a blur.
Try it with a camera fixed on a tripod and experiment with different shutter speeds.
Thus when there is movement in the scene:
A slow shutter speed (long exposure) will record this movement into what is called “motion blur”, but onto one image.
A fast shutter speed (short exposure) will freeze the movement.
Camera shake: It’s important to note that slow shutter speeds cannot be done handheld because your photo will be blurred due to vibration from camera shake. No matter how steady you think you are holding your camera, it’s probably not enough.
Minimum handheld shutter speed = 1/125 sec
This is what I consider to be the best speed to use handheld. But a lot also depends on your equipment, and the conditions you are working in.
- If it’s cold, you will shiver.
- If your equipment is heavy (big long lens), you will struggle to hold it still.
- If you are working in an awkward place, or your having to stand tiptoe or crouch down for your shot, it will be harder to hold the camera steady.
For zoom or telephoto lenses, the rule of thumb is to shoot at a shutter speed equal to or higher than the focal length.
IE: 500mm = 1/500 sec
But of course it also depends on the type of lens. A cheap lightweight zoom will be easier to hold still than an expensive top of the range lens, which is larger and heavier.
The following image was shot handheld at 1/400 at 380mm using the lens in the previous photo. It’s a heavy lens, and so is the camera, so I took no chances.
Image stabilisation/Vibration Reduction
Many of today’s lenses have the above feature which allows you to shoot handheld at slightly lower shutter speeds. However, it usually only allows about two stops below normal, and again comes with a compromise: Softens the image. This might be acceptable for some portraits, but definitely not for landscapes.
Tripod or increased shutter speed?
Shutter speeds below around 1/125 sec (depending on how steady your hand is or how heavy your camera is) typically need a tripod, or some other form of support to keep the camera from moving. Even the slightest movement or vibration will cause unwanted blurring in your image and a loss of sharpness.
You can also use a beanbag when shooting over walls, from car windows or on the floor. When shooting in low light or in conditions that require a long exposure, we want to keep the image sharp and free from blurring due to vibration. So the only way to do this is to increase the shutter speed, or use a tripod.
However, a tripod can only be used if your scene is still. If people are in your scene then they will be blurred, even if they are standing still. Like with holding a camera still, people cannot stand perfectly still no matter how hard they try.
Also watch out for leaves or grass blowing in the wind, or boats floating on water (unless you want this effect). Study your scene to see if using a tripod will work, or whether you have to increase the shutter speed.
Important note: If you are using a fast shutter speed, a tripod or other support, make sure you turn off the image stabilisation function. If you don’t then your image will be blurred because the camera assumes there is camera shake when it’s on and tried to compensate regardless. If there is no camera shake, then it will create it.
Unwanted Motion Blur
Although setting the right shutter speed avoids camera shake blur, there is also the problem of motion blur when it’s not wanted. When people, especially children and babies, are moving then you need to consider how fast they are moving and increase the shutter speed accordingly.
1/60 sec (moving foot and hand are blurred)
Although this was shot with the image stabiliser switched on to avoid camera shake, moving subjects can also cause blur when the shutter speed is too slow.
You either need to increase the shutter speed to at least 1/200 sec in a situation like this, or keep the subject still (not so easy with babies!)
Avoiding Unwanted Motion Blur
In order to avoid this problem, you either need to increase your shutter speed to freeze the movement, or like I did here, be patient and wait for the movement to stop, then be ready to quickly take your shot. Sometimes the situation won’t allow for a faster shutter speed.
Unavoidable Motion Blur
Sometimes it’s simply not possible to avoid. On this photo taken during the low light of dawn a long exposure was needed. Even though it was morning and the lake was still, there was still some slight drifting of the boats. I exposed for 20 seconds praying for as little movement as possible. Only the boats on the far left and right moved enough to create some blur. But overall I think the effect worked quite well.
Long exposures (creative blur)
Sometimes we want to use blur in our images to creative effect. This is especially true with water, clouds and even people or vehicles. Here are a few examples, again all shot on a tripod.
Fast flowing water becomes smooth and silky during long exposures
In the next photo, a shorter exposure has partially frozen the water but still left some sense of movement.
This much longer exposure has created a dreamy effect on the water.
Long exposures create a misty effect from the crashing waves on the sea
The longer exposure also added cloud movement
This very long exposure has created super long cloud movement and some star trails
Even though this is a fast shutter speed, as the duck’s wings are beating extremely fast this was just the right speed to create a slight motion blur on the wings
Medium shutter speed along with panning produce dramatic sports/action shots
The slow shutter speed here has not only been used to smooth out the sea, but also to blur the grass blowing in the wind.
A Great example of how light draws our image
Ghost image – During a long exposure when a subject is not in the frame for the full exposure period then we can get ghosting.
During this 30 sec exposure I stood in the frame for about 25 sec then moved away (very fast). As I was present for most of the exposure the light had started to draw me on the sensor, but because I moved away before the exposure time was up, it started drawing what was behind me. Therefore we ended up with an opaque picture of me in the scene.
However for ghosting or blurring to happen, the subject must be in the frame for enough of the exposure time, otherwise the person or people will be erased or not drawn. For example, if you set up a tripod in a busy train station where people are constantly walking past, and use a very long exposure then the result will be a picture of an empty train station. Also when shooting a street at night and someone walks in front of the camera, they will not appear on the photo if the exposure was long, say several seconds.
Practice effects like ghosting at night or in the evening, using yourself as the subject. Use the camera’s timer to start.
Fast exposures – freezing your subject
Fast shutter speeds will freeze any movement in your photo. How fast a shutter speed is required very much depends on the following things:
- How fast your subject is actually moving
- How fast it appears to be moving
The latter may sound a bit strange, but it’s all about perspective. Next time you are out get a friend to run, first parallel to you (across the width of the frame, like the boy in the photo), then towards you at the same speed. You’ll see that when the person is coming towards you, it doesn’t seem so fast.
Obviously the horses were running much faster than the boy, but as they were moving in my direction, towards me, 1/800 sec was fast enough to freeze the action.
This article is an extract from my free e-book here