Techniques Optical image stabilization Ī comparison of close-up photographs of a calculator keypad with and without optical image stabilizationĪn optical image stabilizer ( OIS, IS, or OS) is a mechanism used in still or video cameras that stabilizes the recorded image by varying the optical path to the sensor. Each method has distinctive advantages and disadvantages. Stabilization can be applied in the lens, or in the camera body. The Pentax K-5 and K-r, when equipped with the O-GPS1 GPS accessory for position data, can use their sensor-shift capability to reduce the resulting star trails. However, fastening it to the Earth is not enough, since the Earth rotates.
Some lenses and camera bodies include a secondary panning mode or a more aggressive 'active mode', both described in greater detail below under optical image stabilization.Īstrophotography makes much use of long-exposure photography, which requires the camera to be fixed in place. Image stabilization is only designed for and capable of reducing blur that results from normal, minute shaking of a lens due to hand-held shooting. However, image stabilization does not prevent motion blur caused by the movement of the subject or by extreme movements of the camera. On a 2× crop factor camera, for instance, a 50 mm lens produces the same field of view as a 100 mm lens used on a 35 mm film camera, and can typically be handheld at 1⁄ 100 second. The latter values are referred to as the crop factor, field-of-view crop factor, focal-length multiplier, or format factor. This means that the 35 mm frame is 1.5, 1.6, or 2 times the size of the digital sensor. For example, many digital SLR cameras use an image sensor that is 2⁄ 3, 5⁄ 8, or 1⁄ 2 the size of a 35 mm film frame. When calculating the effective focal length, it is important to take into account the image format a camera uses. The sharpness obtainable at a given speed can increase dramatically. As a result of the 2-to-4.5-stops slower shutter speeds allowed by IS, an image taken at 1⁄ 125 second speed with an ordinary lens could be taken at 1⁄ 15 or 1⁄ 8 second with an IS-equipped lens and produce almost the same quality. For example, at a focal length of 125 mm on a 35 mm camera, vibration or camera shake could affect sharpness if the shutter speed is slower than 1⁄ 125 second. In photography, image stabilization can facilitate shutter speeds 2 to 5.5 stops slower (exposures 4 to 22 + 1⁄ 2 times longer), and even slower effective speeds have been reported.Ī rule of thumb to determine the slowest shutter speed possible for hand-holding without noticeable blur due to camera shake is to take the reciprocal of the 35 mm equivalent focal length of the lens, also known as the "1/mm rule".
Though the exposure time of 1⁄ 4 s at (35 mm equivalent) 180 mm focal length would typically result in a relatively strong blur according to the "1/mm rule", the image is quite sharp – which is the result of the activated image stabilizer of the employed Lumix digital camera. Photography of a sound reinforcement system prior to a pop concert, wherein the room was nearly dark except for the blue spotlight and the dim white light from the device rear panel itself.
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