For When Things Are a Little Shaky
Canon defines camera shake as: “A term used to define the act of accidentally shaking a camera during shooting due to unsteady hands, which results in blurry images. This generally occurs more often if you’re shooting on a low shutter speed or with a heavy lens”.
To overcome camera shake, the general rule of thumb is to select a shutter speed that is faster than the reciprocal of the focal length of the lens. Simply put, to minimise the camera shake of a 600mm lens, a shutter speed of 1/600th of a second or faster should be selected. If you are using a crop sensor camera then you base your shutter speed on the ‘effective focal length’ of the lens. Again, using our 600mm lens as an example, on a crop sensor camera your shutter speed on a camera with a 1.6x crop factor, your shutter speed should be 1/960th or faster.
There are times when we need to shoot with a shutter speed that is slower than the ‘reciprocal rule’ which can sometimes be achieved by mounting the camera on a tripod, but not always. On those occasions we need to understand what can be achieved with the Image Stabilisation feature.
Image Stabilisation – different manufactures refer to it by different names, Canon and Olympus use the term Image Stabilisation (IS), Nikon refers to it as Vibration Reduction (VR) and Sigma refers to it as Optical Stabilisation (OS). Regardless of the term used to describe it, Image Stabilisation is a technology that is included in most quality telephoto lenses and in some cameras, that has been developed to counteract the effects of camera shake. We won’t get into the detail of the technology itself, but will offer some guidelines on its use. The use of image stabilisation is another one of those contentious issues you will find on the web with a wide variety of opinions. I do not profess that what I am outlining in regards to image stabilisation is the only and right way, but simply that what I have found has worked for me. It is critical that you explore and test your own equipment to discover what the best options for you are.
The amount of compensation offered by Image Stabilisation varies from lens to lens. Some manufactures claim between 2 to 5 stops of stabilisation. This means that you should be able to shoot handheld with a 600mm lens at 1/50th of a second. Of course, the weight of the lens, distance to the bird and your steadiness are also factors to consider. The use of image stabilisation should be employed at all times when handholding your camera, but what about when it is mounted on a tripod?
The general advice is that Image Stabilisation should be turned off when using shutter speeds faster than the reciprocal of the focal length or when the camera is mounted on a tripod as it may cause more harm than good. I have found that this general advice is not as straightforward as it appears and my experience has been slightly contradictory to the advice.
Regarding the use of IS at higher shutter speeds, whilst it may not be necessary to counteract camera shake in the image captured on the sensor at high speeds, it can be very helpful in stabilising the image in the viewfinder to assist in achieving and maintaining your focus point on the subject. It will assist the Auto Focus mechanics of the camera.
Turn IS On or Off when mounted on a Tripod?
As a general rule, it is recommended that IS should be turned off when the camera is mounted on the tripod, but is that sound advice?
The effectiveness of using IS when the camera is mounted on the tripod is a hotly debated topic that I feel needs a little clarification. The advice from many is that when the camera is locked down on the tripod head IS should be turned off to prevent the IS from adding movement when none exists. When using a gimbal head however, the camera is not locked down and can continue to experience camera shake despite being mounted on a tripod and therefore, IS should be left on.
Many of today’s modern lenses are also “tripod aware” and the image stabilisation is not initiated when it is not needed.
It is ideal to spend a bit of time analysing the performance of your Image Stabilisation capabilities before heading out to the field. Identify the lowest shutter speed you are able to use with the camera handheld with Image Stabilisation on at the longest focal length of your lens. Also spend time determining how effective your image stabilisation is when the camera is mounted on a tripod of monopod.
A last note on Image Stabilisation – it is only effective in counteracting camera shake – it has no effect in eliminating the motion of a moving subject, this is controlled solely by the selected shutter speed.