The phenomenon known as camera shake is caused by movement of the camera (hence the name, which becomes noticeable as blur when using a slow shutter speed. The resulting blur is not quite the same as the blur caused by incorrect focusing. How can we tell the difference between blurred focus and camera shake?
Have a look at the picture on the left. Here we have a mixture of blur caused by the subject moving, blur caused by the camera moving and the blur of the background which is out of focus. The focus is actually sharp on the main subject, but you’ll have to take my word for that. You can see the difference between the two types of blur if you look closely, rather than a general fuzziness, movement blur looks more like a double exposure or a series of exposures. If you look at the back wall in this first picture you can see both types of blur. The wall is ‘soft’ due to being out of focus but also there is a double, or triple, image which is caused by camera movement.
Motion blur, whether it is caused by movement of the subject or movement of the camera, looks the same. Although some of the movement is caused by the guitarist moving, the microphone, which wasn’t moving, is blurred too, as is the background, this is due to camera shake.
Take a look a this second photo, The photo is now generally sharp because I have used a flash, and therefore a much faster shutter speed, but the wall is still blurred because it is out of focus. I think if you look at the green tiles in both pictures you can see the different types of blur quite clearly.
Whereas blur caused by movement of the subject can be desirable, sometimes, to help create ‘atmosphere’ in a picture, camera shake should be avoided in all but the most ‘arty’ type of photos.
Why do we get camera shake?
No matter how careful we are, when we press the shutter button there is always some movement of the camera. At faster shutter speeds there is no noticeable effect on the picture but at slower speeds the blur becomes apparent. The way we stand, the way we hold the camera and how vigorously we press the shutter button all have an effect on the amount of movement we get.
How can we avoid movement blur from camera shake?
To eliminate the blur we can do several things:-
- Use a faster shutter speed and/or a shorter lens.
- Use a tripod with or without a remote release.
- Brace ourselves as best we can against a wall or other object to minimize movement.
1) The most obvious way of eliminating shake is to use a faster shutter speed. Either by opening the aperture wider or introducing more light by using a flash gun for instance.
The rule of thumb for a sharp picture, free from the effects of camera shake, is to use a shutter speed which is at least as fast as 1 divided by the focal length of the lens. So if you are using your zoom set at 100mm you should use a shutter speed of at least 1/100 of a second. If you are using a 50mm lens you will get a sharp picture at 1/50th of a second.
The reason why the focal length of the lens is important is that camera shake becomes more apparent as the angle of view gets narrower, the narrower the angle of view the more the shake is magnified. You will know this if you have ever tried to hold a telescope or a high powered pair of binoculars still.
2) Putting the camera on a sturdy tripod is the best way to keep it still and this is the way to go, especially when you want to get some movement blur from the subject like in the waterfall picture here. Even better is to get a remote release for the camera so you don’t have to touch it at all.
3) If, like me, you didn’t bring your tripod with you and you still want to take pictures in the dark, you can stretch the rule of thumb (above) by a few stops by bracing yourself and/or the camera against a tree or wall or lamppost. Also controlling your breathing can help quite a bit too. Here’s a picture shot at a slow shutter speed using this technique.
Finally I just want to say that an inherent problem with a lot of today’s smaller cameras, especially phone cameras, is that, because they have no viewfinder, we are obliged to hold them at arm’s length to view the screen, often holding them only with our fingertips. This makes them infinitely more difficult to hold still and makes them much more prone to show the effects of camera shake. So even more care needs to be taken to get a sharp picture. If you are taking a picture with a phone camera (if you really must!), try to rest it on something, a table or wall, to help keep it still.