Image stabilization
Encyclopedia
Image stabilization is a family of techniques used to reduce blurring associated with the motion of a camera during exposure. Specifically, it compensates for pan and tilt (angular movement, equivalent to yaw and pitch) of a camera or other imaging device. It is used in image-stabilized binoculars
, still
and video
cameras, and astronomical telescope
s. With still camera
s, camera shake is particularly problematic at slow shutter speed
s or with long focal length (telephoto
) lenses. With video camera
s, camera shake causes visible frame-to-frame jitter
in the recorded video. In astronomy, the problem of lens-shake is added to by variations in the atmosphere over time, which cause the apparent positions of objects to change.
The 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 35mm equivalent
focal length of the lens. For example, at a focal length of 125 mm on a 35mm camera, vibration or camera shake could affect sharpness if the shutter speed was slower than 1/125 second. As a result of the 3–4 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. The sharpness obtainable at a given speed can increase dramatically.
When calculating the effective focal length, it is important to take into account the image format a camera uses. For example, many digital SLR cameras use an image sensor that is 2/3, 5/8, or 1/2 the size of a 35mm film frame. This means that the 35 mm frame is 1.5, 1.6, or 2 times the size of the digital sensor. The latter values are referred to as the crop factor
, field-of-view crop factor, focal-length multiplier, or format factor. On a 2x crop factor camera, for instance, a 50mm lens produces the same field of view as a 100mm lens used on a 35mm film camera, and can typically be handheld at 1/100 of a second.
However, image stabilization does not prevent motion blur
caused by the movement of the subject or by extreme movements of the camera. 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. 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.
Image-stabilization features can also be a benefit in astrophotography
, when the camera is technically- but not effectively- fixed in place. The Pentax K-5 and K-r can use their sensor-shift capability to reduce star trails in reasonable exposure times, when equipped with a GPS accessory
for position data. In effect, the stabilization compensates for the Earth's motion, not the camera's.
There are two types of implementation - lens-based, or body-based stabilization. These refer to where the stabilizing system is located. Both have their advantages and disadvantages.
An optical image stabilizer, often abbreviated OIS, IS, or OS, is a mechanism used in a still camera or video camera that stabilizes the recorded image by varying the optical path to the sensor. This technology is implemented in the lens itself, or by moving the sensor as the final element in the optical path. The key element of all optical stabilization systems is that they stabilize the image projected on the sensor before the sensor converts the image into digital
information.
Different companies have different names for the OIS technology; for example: Image Stabilization (IS - Canon, the first to produce an OIS lens), Vibration Reduction (VR - Nikon
), Optical SteadyShot
(Sony Cyber-Shot), MegaOIS (Panasonic
and Leica), Super Steady Shot (SSS - Sony
), Optical Stabilization (OS - Sigma
), Vibration Compensation (VC - Tamron
) and Shake Reduction (SR - Pentax
).
using electromagnets. Vibration is detected using two piezoelectric angular velocity
sensors (often called gyroscopic
sensors), one to detect horizontal movement and the other to detect vertical movement. As a result, this kind of image stabilizer only corrects for pitch and yaw axis rotations, and cannot correct for rotation around the optical axis. Some lenses have a secondary mode that counteracts vertical camera shake only. This mode is useful when using a panning
technique, and switching into this mode depends on the lens; sometimes it is done by using a switch on the lens, or it can be automatic.
Some of Nikon's more recent VR-enabled lenses offer an 'Active Mode' that is intended to be used when shooting from a moving vehicle, such as a car or boat, and should correct for larger shakes than the 'Normal Mode'. However, Active Mode, when used under normal shooting conditions, can result in poorer results than the 'Normal Mode'.
This is because active mode is optimized for reducing higher angular velocity movements (typically when shooting from a heavily moving platform using faster shutter speeds), where normal mode tries to reduce lower angular velocity movements over a larger ampliture and timeframe (typically body and hand movement when standing on a stationary or slowly moving platform while using slower shutter speeds).
Most manufacturers suggest that the IS feature of a lens be turned off when the lens is mounted on a tripod as it can cause erratic results and is generally unnecessary. Many modern image stabilization lenses (notably Canon's more recent IS lenses) are able to auto-detect that they are tripod-mounted (as a result of extremely low vibration readings) and disable IS automatically to prevent this and any consequent image quality reduction. The system also draws power from the battery, so de-activating it when it is not needed will extend the time before a recharge is required.
One of the main disadvantages about lens-based image stabilization is the higher price tag that comes with it; image stabilisation has to be paid for each lens anew. Also, not every lens is available as an image-stabilised variant. This is often the case for fast primes and wide-angle lenses. While the most obvious advantage for image stabilisation lies with longer focal lengths, even normal and wide-angle lenses benefit from it in low-light applications. Furthermore, because light passing through the lens is shifted from its true optical path when it projects out the rear element onto the sensor, poor 'bokeh
' can result. However, this could be considered and compensated during the design stage of the lens.
Lens based stabilization also has advantages over in-body stabilization. In low-light or low-contrast situations, the autofocus system (which has no stabilized sensors) is able to work more accurately when the image coming from the lens is already stabilized. In cameras with optical viewfinders, the image seen by the photographer through the stabilized lens (as opposed to in-body stabilization) reveals more detail because of its stability, and it also makes correct framing easier. This is especially the case with longer telephoto lenses.
used a technique called "anti-shake" now marketed as SteadyShot
in the Sony α line and "shake reduction - SR" in the K-5, K-7, K10D, K20D, K100D, K200D, K-m (K-2000) and K-x lines by Pentax
, which relies on a very precise angular rate sensor to detect camera motion. Olympus
introduced image stabilization with their E-510
D-SLR
body, employing a system built around their Supersonic Wave Drive. Other manufacturers use DSP
s to analyze the image on the fly and then move the sensor appropriately. Sensor shifting is also used in some cameras by Fujifilm, Pentax, Samsung, Casio Exilim and Ricoh Caplio.
The advantage with moving the image sensor
, instead of the lens, is that the image will be stabilized regardless of what lens is being used. This allows the stabilization to work with any lens the photographer chooses and reduces the weight and complexity of the lenses. Further, when sensor-based image stabilization technology improves, it only requires replacing the camera to take advantage of the improvements, which is typically far less expensive than replacing all existing lenses if relying on lens-based image stabilization. Some sensor-based image stabilization implementations are capable of correcting camera roll
rotation, a motion that is easily excited by pressing the shutter button. No lens-based system can address this potential source of image blur. A by-product of available "roll" compensation is that the camera can automatically correct for tilted horizons in the optical domain, provided it is equipped with an electronic spirit level, such as the Pentax K-7/K-5 cameras.
One of the primary disadvantages of moving the image sensor itself is that the image projected to the viewfinder is not stabilized. However, this is not an issue on cameras that use an electronic viewfinder
(EVF), since the image projected on that viewfinder is taken from the image sensor itself. Similarly, the image projected to a phase-detection autofocus system, if used, is not stabilized.
In-body image stabilization requires the lens to have a larger output image circle because the sensor is moved during exposure and thus uses a larger part of the image. Compared to lens movements in optical image stabilisation systems the sensor movements are quite large, so the effectiveness is limited by the maximum range of sensor movement, where a typical modern optically stabilized lens has greater freedom. The required sensor movement (both speed and range) increase with the focal length of the lens being used, making sensor-shift technology less suited for very long telephoto lenses, especially when using slower shutter speeds because the available motion range of the sensor quickly becomes insufficient to cope with the increasing image displacement.
Unfortunately, many still camera manufacturers market their cameras as having "digital image stabilization", when they really only have a mode with a sub-optimal image exposure time, resulting in pictures with less motion blur, but more noise.
The main disadvantage with this solution is that motion blur from shake under medium to low light conditions will be impossible to correct by the post processing images stabilization system, so in real life this will only work well for short exposure times (daylight).
s use stabilization filters
that can correct a non-stabilized image by tracking the movement of pixels in the image and correcting the image by moving the frame. The process is similar to digital image stabilization but since there is no larger image to work with the filter either crops the image down to hide the motion of the frame or attempts to recreate the lost image at the edge through spatial or temporal extrapolation
.
itself while the image is being captured, based on analysis of the apparent motion of bright stars. This is a rare example of digital stabilization for still pictures. An example of this is in the upcoming gigapixel telescope Pan-STARRS
being constructed in Hawaii.
to the camera body, usually utilizing the camera's built-in tripod mount. This allows the external gyro to stabilize the camera, and is typically employed in photography from a moving vehicle, when a lens or camera offering another type of image stabilization is not available.
Another technique for stabilizing a video or motion picture camera body is the Steadicam
system which isolates the camera from the operator's body using a harness and a camera boom with a counterweight.
functions as the biological analogue of an accelerometer
in camera image stabilization systems, to stabilize the image by moving the eyes
. When a rotation of the head is detected, an inhibitory signal is sent to the extraocular muscles on one side and an excitatory signal to the muscles on the other side. The result is a compensatory movement of the eyes. Typically eye movements lag the head movements by less than 10 ms.
Image-stabilized binoculars
Image-stabilized binoculars are binoculars that have a mechanism for decreasing the apparent motion of the view due to binocular movement.Image stabilized binoculars are designed to minimize image shaking in hand-held binoculars. Higher power binoculars bring the image closer, but the image shift...
, still
Digital camera
A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...
and video
Video camera
A video camera is a camera used for electronic motion picture acquisition, initially developed by the television industry but now common in other applications as well. The earliest video cameras were those of John Logie Baird, based on the electromechanical Nipkow disk and used by the BBC in...
cameras, and astronomical telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
s. With still camera
Still camera
A still camera is a type of camera used to take photographs. Traditional cameras capture light onto photographic film. Digital cameras use electronics, usually a charge coupled device to store digital images in computer memory inside the camera...
s, camera shake is particularly problematic at slow shutter speed
Shutter speed
In photography, shutter speed is a common term used to discuss exposure time, the effective length of time a camera's shutter is open....
s or with long focal length (telephoto
Telephoto lens
In photography and cinematography, a telephoto lens is a specific type of a long-focus lens in which the physical length of the lens is shorter than the focal length. This is achieved by incorporating a special lens group known as a telephoto group that extends the light path to create a long-focus...
) lenses. With video camera
Video camera
A video camera is a camera used for electronic motion picture acquisition, initially developed by the television industry but now common in other applications as well. The earliest video cameras were those of John Logie Baird, based on the electromechanical Nipkow disk and used by the BBC in...
s, camera shake causes visible frame-to-frame jitter
Jitter (optics)
In optics, jitter is used to refer to motion that has high temporal frequency relative to the integration/exposure time. This may result from vibration in an assembly or from the unstable hand of a photographer. Jitter is typically differentiated from smear, which has a lower frequency relative...
in the recorded video. In astronomy, the problem of lens-shake is added to by variations in the atmosphere over time, which cause the apparent positions of objects to change.
Application in still photography
In photography, image stabilization can often permit the use of shutter speeds 2–4 stops slower (exposures 4–16 times longer), although even slower effective speeds have been reported.The rule of thumb
Rule of thumb
A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination...
to determine the slowest shutter speed possible for hand-holding without noticeable blur due to camera shake is to take the reciprocal
Multiplicative inverse
In mathematics, a multiplicative inverse or reciprocal for a number x, denoted by 1/x or x−1, is a number which when multiplied by x yields the multiplicative identity, 1. The multiplicative inverse of a fraction a/b is b/a. For the multiplicative inverse of a real number, divide 1 by the...
of the 35mm equivalent
Crop factor
In digital photography, a crop factor is related to the ratio of the dimensions of a camera's imaging area compared to a reference format; most often, this term is applied to digital cameras, relative to 35 mm film format as a reference. In the case of digital cameras, the imaging device would be a...
focal length of the lens. For example, at a focal length of 125 mm on a 35mm camera, vibration or camera shake could affect sharpness if the shutter speed was slower than 1/125 second. As a result of the 3–4 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. The sharpness obtainable at a given speed can increase dramatically.
When calculating the effective focal length, it is important to take into account the image format a camera uses. For example, many digital SLR cameras use an image sensor that is 2/3, 5/8, or 1/2 the size of a 35mm film frame. This means that the 35 mm frame is 1.5, 1.6, or 2 times the size of the digital sensor. The latter values are referred to as the crop factor
Crop factor
In digital photography, a crop factor is related to the ratio of the dimensions of a camera's imaging area compared to a reference format; most often, this term is applied to digital cameras, relative to 35 mm film format as a reference. In the case of digital cameras, the imaging device would be a...
, field-of-view crop factor, focal-length multiplier, or format factor. On a 2x crop factor camera, for instance, a 50mm lens produces the same field of view as a 100mm lens used on a 35mm film camera, and can typically be handheld at 1/100 of a second.
However, image stabilization does not prevent motion blur
Motion blur
Motion blur is the apparent streaking of rapidly moving objects in a still image or a sequence of images such as a movie or animation. It results when the image being recorded changes during the recording of a single frame, either due to rapid movement or long exposure.- Photography :When a camera...
caused by the movement of the subject or by extreme movements of the camera. 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. Some lenses and camera bodies include a secondary panning
Panning (camera)
In photography, panning refers to the horizontal movement or rotation of a still or video camera, or the scanning of a subject horizontally on video or a display device...
mode or a more aggressive 'active mode', both described in greater detail below under optical image stabilization.
Image-stabilization features can also be a benefit in astrophotography
Astrophotography
Astrophotography is a specialized type of photography that entails recording images of astronomical objects and large areas of the night sky. The first photographs of an astronomical object were taken in the 1840s, but it was not until the late 19th century that advances in technology allowed for...
, when the camera is technically- but not effectively- fixed in place. The Pentax K-5 and K-r can use their sensor-shift capability to reduce star trails in reasonable exposure times, when equipped with a GPS accessory
GeoTagging
Geotagging is the process of adding geographical identification metadata to various media such as a geotagged photograph or video, websites, SMS messages, QR Codes or RSS feeds and is a form of geospatial metadata...
for position data. In effect, the stabilization compensates for the Earth's motion, not the camera's.
There are two types of implementation - lens-based, or body-based stabilization. These refer to where the stabilizing system is located. Both have their advantages and disadvantages.
Optical image stabilization
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
information.
Different companies have different names for the OIS technology; for example: Image Stabilization (IS - Canon, the first to produce an OIS lens), Vibration Reduction (VR - Nikon
Nikon
, also known as just Nikon, is a multinational corporation headquartered in Tokyo, Japan, specializing in optics and imaging. Its products include cameras, binoculars, microscopes, measurement instruments, and the steppers used in the photolithography steps of semiconductor fabrication, of which...
), Optical SteadyShot
SteadyShot
SteadyShot is the trademarked name of an integrated video camera image stabilisation technology developed by Sony for its range of consumer and prosumer video camcorders...
(Sony Cyber-Shot), MegaOIS (Panasonic
Panasonic
Panasonic is an international brand name for Japanese electric products manufacturer Panasonic Corporation, which was formerly known as Matsushita Electric Industrial Co., Ltd...
and Leica), Super Steady Shot (SSS - Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
), Optical Stabilization (OS - Sigma
Sigma Corporation
is a Japanese company founded in 1961, manufacturing cameras, lenses, flashes and other photographic accessories. All Sigma products are produced in the company's own Aizu factory in Bandai, Fukushima, Japan...
), Vibration Compensation (VC - Tamron
Tamron
is a Japanese company manufacturing photographic lenses, optical components and commercial/industrial-use optics. Tamron Headquarters is located in Saitama City in the Saitama Prefecture of Japan....
) and Shake Reduction (SR - Pentax
Pentax
Pentax is a brand name used by Hoya Corporation for its medical-related products & services and Pentax Ricoh Imaging Company for cameras, sport optics , etc. Hoya purchased and merged with the Japanese optics company on March 31, 2008. Hoya's Pentax imaging business was sold to Ricoh Company, Ltd...
).
Lens-based
In Nikon and Canon's implementation, it works by using a floating lens element that is moved orthogonally to the optical axis of the lensPhotographic lens
A camera lens is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.While in principle a simple convex lens will suffice, in...
using electromagnets. Vibration is detected using two piezoelectric angular velocity
Angular velocity
In physics, the angular velocity is a vector quantity which specifies the angular speed of an object and the axis about which the object is rotating. The SI unit of angular velocity is radians per second, although it may be measured in other units such as degrees per second, revolutions per...
sensors (often called gyroscopic
Gyroscope
A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...
sensors), one to detect horizontal movement and the other to detect vertical movement. As a result, this kind of image stabilizer only corrects for pitch and yaw axis rotations, and cannot correct for rotation around the optical axis. Some lenses have a secondary mode that counteracts vertical camera shake only. This mode is useful when using a panning
Panning (camera)
In photography, panning refers to the horizontal movement or rotation of a still or video camera, or the scanning of a subject horizontally on video or a display device...
technique, and switching into this mode depends on the lens; sometimes it is done by using a switch on the lens, or it can be automatic.
Some of Nikon's more recent VR-enabled lenses offer an 'Active Mode' that is intended to be used when shooting from a moving vehicle, such as a car or boat, and should correct for larger shakes than the 'Normal Mode'. However, Active Mode, when used under normal shooting conditions, can result in poorer results than the 'Normal Mode'.
This is because active mode is optimized for reducing higher angular velocity movements (typically when shooting from a heavily moving platform using faster shutter speeds), where normal mode tries to reduce lower angular velocity movements over a larger ampliture and timeframe (typically body and hand movement when standing on a stationary or slowly moving platform while using slower shutter speeds).
Most manufacturers suggest that the IS feature of a lens be turned off when the lens is mounted on a tripod as it can cause erratic results and is generally unnecessary. Many modern image stabilization lenses (notably Canon's more recent IS lenses) are able to auto-detect that they are tripod-mounted (as a result of extremely low vibration readings) and disable IS automatically to prevent this and any consequent image quality reduction. The system also draws power from the battery, so de-activating it when it is not needed will extend the time before a recharge is required.
One of the main disadvantages about lens-based image stabilization is the higher price tag that comes with it; image stabilisation has to be paid for each lens anew. Also, not every lens is available as an image-stabilised variant. This is often the case for fast primes and wide-angle lenses. While the most obvious advantage for image stabilisation lies with longer focal lengths, even normal and wide-angle lenses benefit from it in low-light applications. Furthermore, because light passing through the lens is shifted from its true optical path when it projects out the rear element onto the sensor, poor 'bokeh
Bokeh
In photography, bokeh is the blur, or the aesthetic quality of the blur, in out-of-focus areas of an image, or "the way the lens renders out-of-focus points of light."...
' can result. However, this could be considered and compensated during the design stage of the lens.
Lens based stabilization also has advantages over in-body stabilization. In low-light or low-contrast situations, the autofocus system (which has no stabilized sensors) is able to work more accurately when the image coming from the lens is already stabilized. In cameras with optical viewfinders, the image seen by the photographer through the stabilized lens (as opposed to in-body stabilization) reveals more detail because of its stability, and it also makes correct framing easier. This is especially the case with longer telephoto lenses.
Sensor-shift
The sensor capturing the image can be moved in such a way as to counteract the motion of the camera, a technology often referred to as mechanical image stabilization. When the camera rotates, causing angular error, gyroscopes encode information to the actuator that moves the sensor. The sensor is moved to maintain the projection of the image onto the image plane, which is a function of the focal length of the lens being used; modern cameras can acquire focal length information from the lens. Konica MinoltaKonica Minolta
is a Japanese manufacturer of office equipment, medical imaging, graphic imaging, optical devices, and measuring instruments. It is headquartered in the Marunouchi Center Building in Marunouchi, Chiyoda, Tokyo, with a Kansai office in Nishi-ku, Osaka, Osaka Prefecture...
used a technique called "anti-shake" now marketed as SteadyShot
SteadyShot
SteadyShot is the trademarked name of an integrated video camera image stabilisation technology developed by Sony for its range of consumer and prosumer video camcorders...
in the Sony α line and "shake reduction - SR" in the K-5, K-7, K10D, K20D, K100D, K200D, K-m (K-2000) and K-x lines by Pentax
Pentax
Pentax is a brand name used by Hoya Corporation for its medical-related products & services and Pentax Ricoh Imaging Company for cameras, sport optics , etc. Hoya purchased and merged with the Japanese optics company on March 31, 2008. Hoya's Pentax imaging business was sold to Ricoh Company, Ltd...
, which relies on a very precise angular rate sensor to detect camera motion. Olympus
Olympus Corporation
is a Japan-based manufacturer of optics and reprography products. Olympus was established on 12 October 1919, initially specializing in microscope and thermometer businesses. Its global headquarters are in Shinjuku, Tokyo, Japan, while its USA operations are based in Center Valley, Pennsylvania,...
introduced image stabilization with their E-510
Olympus E-510
The Olympus E-510 is a 10 megapixel digital single-lens reflex camera oriented to the "prosumer" or "hobbyist" market. Announced in March 2007 to succeed the E-500, it represents the first use of the new Panasonic MOS sensors instead of the Kodak CCD sensors that Olympus had used previously...
D-SLR
Digital single-lens reflex camera
Most digital single-lens reflex cameras are digital cameras that use a mechanical mirror system and pentaprism to direct light from the lens to an optical viewfinder on the back of the camera....
body, employing a system built around their Supersonic Wave Drive. Other manufacturers use DSP
Digital signal processor
A digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...
s to analyze the image on the fly and then move the sensor appropriately. Sensor shifting is also used in some cameras by Fujifilm, Pentax, Samsung, Casio Exilim and Ricoh Caplio.
The advantage with moving the image sensor
Image sensor
An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...
, instead of the lens, is that the image will be stabilized regardless of what lens is being used. This allows the stabilization to work with any lens the photographer chooses and reduces the weight and complexity of the lenses. Further, when sensor-based image stabilization technology improves, it only requires replacing the camera to take advantage of the improvements, which is typically far less expensive than replacing all existing lenses if relying on lens-based image stabilization. Some sensor-based image stabilization implementations are capable of correcting camera roll
Flight dynamics
Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control systems for...
rotation, a motion that is easily excited by pressing the shutter button. No lens-based system can address this potential source of image blur. A by-product of available "roll" compensation is that the camera can automatically correct for tilted horizons in the optical domain, provided it is equipped with an electronic spirit level, such as the Pentax K-7/K-5 cameras.
One of the primary disadvantages of moving the image sensor itself is that the image projected to the viewfinder is not stabilized. However, this is not an issue on cameras that use an electronic viewfinder
Electronic viewfinder
An electronic viewfinder or EVF is a viewfinder where the image captured by the lens is projected electronically onto a miniature display. The image on this display is used to assist in aiming the camera at the scene to be photographed.-Operation:...
(EVF), since the image projected on that viewfinder is taken from the image sensor itself. Similarly, the image projected to a phase-detection autofocus system, if used, is not stabilized.
In-body image stabilization requires the lens to have a larger output image circle because the sensor is moved during exposure and thus uses a larger part of the image. Compared to lens movements in optical image stabilisation systems the sensor movements are quite large, so the effectiveness is limited by the maximum range of sensor movement, where a typical modern optically stabilized lens has greater freedom. The required sensor movement (both speed and range) increase with the focal length of the lens being used, making sensor-shift technology less suited for very long telephoto lenses, especially when using slower shutter speeds because the available motion range of the sensor quickly becomes insufficient to cope with the increasing image displacement.
Digital image stabilization
Real-time digital image stabilization is used in some video cameras. This technique shifts the electronic image from frame to frame of video, enough to counteract the motion. It uses pixels outside the border of the visible frame to provide a buffer for the motion. This technique reduces distracting vibrations from videos or improves still image quality by allowing one to increase the exposure time without blurring the image. This technique does not affect the noise level of the image, except in the extreme borders when the image is extrapolated.Unfortunately, many still camera manufacturers market their cameras as having "digital image stabilization", when they really only have a mode with a sub-optimal image exposure time, resulting in pictures with less motion blur, but more noise.
The main disadvantage with this solution is that motion blur from shake under medium to low light conditions will be impossible to correct by the post processing images stabilization system, so in real life this will only work well for short exposure times (daylight).
Stabilization filters
Many non-linear editing systemNon-linear editing system
In video, a non-linear editing system is a video editing or audio editing digital audio workstation system which can perform random access non-destructive editing on the source material...
s use stabilization filters
Filter (software)
A filter is a computer program to process a data stream. Some operating systems such as Unix are rich with filter programs. Even Windows has some simple filters built into its command shell, most of which have significant enhancements relative to the similar filter commands that were available in...
that can correct a non-stabilized image by tracking the movement of pixels in the image and correcting the image by moving the frame. The process is similar to digital image stabilization but since there is no larger image to work with the filter either crops the image down to hide the motion of the frame or attempts to recreate the lost image at the edge through spatial or temporal extrapolation
Extrapolation
In mathematics, extrapolation is the process of constructing new data points. It is similar to the process of interpolation, which constructs new points between known points, but the results of extrapolations are often less meaningful, and are subject to greater uncertainty. It may also mean...
.
Orthogonal transfer CCD
Used in astronomy, an orthogonal transfer CCD (OTCCD) actually shifts the image within the CCDCharge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
itself while the image is being captured, based on analysis of the apparent motion of bright stars. This is a rare example of digital stabilization for still pictures. An example of this is in the upcoming gigapixel telescope Pan-STARRS
Pan-STARRS
The Panoramic Survey Telescope and Rapid Response System is a planned array of astronomical cameras and telescopes and computing facility that will survey the sky on a continual basis, including accurate astrometry and photometry of detected objects...
being constructed in Hawaii.
Stabilizing the camera body
A technique that requires no additional capabilities of any camera body–lens combination consists of stabilizing the entire camera body externally rather than using an internal method. This is achieved by attaching a gyroscopeGyroscope
A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...
to the camera body, usually utilizing the camera's built-in tripod mount. This allows the external gyro to stabilize the camera, and is typically employed in photography from a moving vehicle, when a lens or camera offering another type of image stabilization is not available.
Another technique for stabilizing a video or motion picture camera body is the Steadicam
Steadicam
A Steadicam is a stabilizing mount for a motion picture camera that mechanically isolates it from the operator's movement, allowing a smooth shot even when moving quickly over an uneven surface...
system which isolates the camera from the operator's body using a harness and a camera boom with a counterweight.
Stabilization in biological eyes
In many animals, including human beings, the inner earInner ear
The inner ear is the innermost part of the vertebrate ear. In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts:...
functions as the biological analogue of an accelerometer
Accelerometer
An accelerometer is a device that measures proper acceleration, also called the four-acceleration. This is not necessarily the same as the coordinate acceleration , but is rather the type of acceleration associated with the phenomenon of weight experienced by a test mass that resides in the frame...
in camera image stabilization systems, to stabilize the image by moving the eyes
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
. When a rotation of the head is detected, an inhibitory signal is sent to the extraocular muscles on one side and an excitatory signal to the muscles on the other side. The result is a compensatory movement of the eyes. Typically eye movements lag the head movements by less than 10 ms.
External links
- Roll test - Video showing a roll test using Cineflex Heligimbal stabilization.
- Norwegian sunrise - behind the scenes - Behind the scenes footage using Heligimbal stabilization.