Shake and stabilization
Camera shake occurs when shooting handheld at ‘slow’ shutter speeds – but how slow depends on the focal length of the lens, and the longer the lens, the greater the effect. The rule of thumb is to shoot ‘one over’ the focal length, so with a 20mm lens you should be able to get shake-free shots at 1/20 sec shutter speed. Shoot with a 200mm lens and you’ll need a shutter speed of at least 1/200 sec. If you’re using a ‘DX’ lens you’ll need to take the 1.5x crop factor into account to calculate the effective focal length – you’ll need to be shooting at 1/300 sec on a 200mm.
Image stabilization – or Vibration Reduction – uses gyroscopes and motors to move a set of lens elements to counter the camera shake, enabling you to shoot at slower shutter speeds. Many of today’s systems can counteract up to four stops of shake, so with the 200mm lens you should be able to get away with shutter speeds as slow as 1/25 sec without shake spoiling a shot. Some lenses have extra stabilization modes to prevent the lens from counteracting the movement of the camera when panning.